Total Synthesis of the Phytopathogen (+)-Fomannosin

TOTAL SYNTHESIS OF THE PHYTOPATHOGEN (+)-FOMANNOSIN

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the Graduate

School of The Ohio State University

Xiaowen Peng, M. S.

*****

The Ohio State University 2006

Dissertation Committee: Approved by Professor Leo A. Paquette, Advisor

Professor David J. Hart ______Professor T. V. RajanBabu Advisor Graduate Program in Chemistry

ABSTRACT

Fomannosin (1) is a sesquiterpene metabolite isolated in 1967 from the medium of the still culture of the wood-rotting fungus, Fomes annosus (Kr.) Karst. It was found to be toxic toward 2-year-old pinus tadae seedlings, Chlorella pyrenoidose, and certain bacteria.

Fomannosin features a unique highly strained methylenecyclobutene unit and a reactive doubly unsaturated lactone. It is very sensitive toward both acid and base, posing a considerable challenge to synthetic chemists.

The enantioselective total synthesis of (+)-fomannosin was completed in 35 steps starting from known tosylate 13. A zirconocene-mediated ring contraction reaction of vinylated furanosides 20 or 21 was utilized to construct the highly substituted cyclobutane 27. The cyclopentene ring was assembled through a ring-closing metathesis reaction. The lactone ring was then installed by a Knoevenagel condensation of thioester

54. Introduction of the cyclopentanone functionality was accomplished through a dihydroxylation, oxidation and SmI2-mediated -deoxygenation reaction sequence to provide lactones 61 and 62.

After the PMB protecting group was removed by trifluoroacetic acid under anhydrous conditions, the first dehydration was effected through the formation of a cyclic

ii sulfite. The second dehydration was achieved through the elimination of trifluoromethanesulfonic acid. Deprotection of the TBS ether led to the isolation of (+)- fomannosin.

iii

Dedicated to my mother Runhua Zhang

and my wife Ling Chen

In memory of my father Xiaoshengmei Peng

ACKNOWLEDGMENTS

I would like to express my sincere gratitude to my advisor, Professor Leo A.

Paquette, for his tremendous support, guidance and encouragement throughout my stay in

Columbus. His dedication and work ethic have had a great influence on me. Without his help, I would not have the opportunity to come back to school, and completing this project would not have been possible.

I wish to thank Professors David J. Hart and T.V. RajanBabu for their willingness to serve on my dissertation committee.

I will always be grateful to a large number of Paquette group members, past and present, for their unconditional help, insightful discussions, and friendship. In particular, I would like to thank Drs. Jiyoung Chang, Maosheng Duan, Ho Yin (Bob) Lo, Feng Geng,

Christopher Seekamp, José Méndez-Andino, John Hofferberth, Fabrice Gallou and

Nicolas Cunière for sharing their experience in the beginning of my graduate studies here, to Drs. Amy Hart, Jizhou Wang and Zuosheng Liu for their suggestions that were crucial to this project., to Yunlong Zhang, Shuzhi Dong, Zhenjiao Tian, Zhimin Du, Dr.

Mike Chang, Dr. Ryan Hartung, Dr. Andreas Luxenburger for their friendship that made my lab life enjoyable.

v I am thankful to Drs. Jiong Yang and Ho-Jung Kang for their pioneering work on this project.

Special thank goes to Dr. Amy Hart and Cate Stewart for proofreading this manuscript, and all the delicious cookies they have brought. I am thankful to Ms. Donna

Rothe and Ms. Rebecca Martin for their kindness and assistance during my stay.

Finally, I wish to thank my mother Runhua Zhang, my wife Ling Chen, and my sisters for their infinite love and support that made all of the above possible.

VITA

August 3, 1974...... Born – Jiangxi, China

1996...... B. S. Chemistry Nankai University

1999...... M. S. Chemistry Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences

1999 – 2000...... Graduate Fellow The Ohio State University

2000 – 2001...... Graduate Research and Teaching Associate The Ohio State University

2001...... M. S. Chemistry The Ohio State University

2002 – 2003...... Research Associate Néokimia Inc., Sherbrooke, Canada

2003 – 2006...... Graduate Teaching Associate The Ohio State University

vii PUBLICATIONS

1. Peng, X.; Bondar, D.; Paquette, L. A. “Alkoxide Precoordination to Rhodium

Enables Stereodirected Catalytic Hydrogenation of a Dihydrofuranol Precursor of the

C29-40 F/G Sector of Pectenotoxin-2” Tetrahedron 2004, 60, 9589.

2. Xu, Q.; Peng, X.; Tian, W. “A New Strategy for Synthesizing the Steroids with

Side Chains from Steroidal Sapogenins: Synthesis of the Aglycone of OSW-1 by Using the Intact Skeleton of Diosgenin” Tetrahedron Lett. 2003, 44, 9375.

3. Paquette, L. A.; Peng, X.; Bondar, D. “Pectenotoxin-2 Synthetic Studies.1.

Alkoxide Precoordination to [Rh(NBD)(DIPHOS-4)]BF4 Allows Directed Hydrogenation of a 2,3-Dihydrofuran-3-ol without Competing Furan Production” Org. Lett. 2002, 4,

937.

4. Kong, D.; Yu, Y.; Jia, Y.; Peng, X.; Wong, J. T. “Mechanism Study of

Haemoglobin Immobilization on Periodated Oxycellulose” Gaofenzi Xuebao 1999, 2,

221.

FIELDS OF STUDY

Major Field: Chemistry

viii

TABLE OF CONTENTS

P a g e

Abstract...... ii

Dedication...... iv

Acknowledgments ...... v

Vita ...... vii

List of Schemes...... xi

List of Figures ...... xiii

List of Tables...... xiv

List of Abbreviations ...... xv

Chapter 1. Introduction ...... 1

1.1. Isolation, Biological Activity, and Structure Determination ...... 1

1.2. Biosynthetic Study ...... 2

1.3. Synthetic Studies on Fomannosin: A Literature Review ...... 3

1.4. Retrosynthetic Analysis ...... 9

Chapter 2. Construction of the Cyclobutane and Cyclopentanone Rings ...... 11

2.1. Synthesis of the Ring Contraction Precursor: Vinylated Furanosides ...... 11

2.2. The Zirconocene-mediated Ring Contraction Reaction ...... 15

ix 2.3. Assembly of the Cyclopentene Ring ...... 17

Chapter 3. Assembly of the Lactone Unit ...... 20

3.1. The Intramolecular Horner-Wadsworth-Emmons Reaction Approach . . . . .20

3.2. The Intramolecular Knoevenagel Condensation Strategy ...... 26

3.2.1. Knoevenagel Condensation with Monoallyl Malonic Ester . . . . . 26

3.2.2. Condensation with Ethylsulfanylcarbonyl Acetic Acid ...... 31

Chapter 4. Completion of the Total Synthesis ...... 35

4.1. PMB Deprotection and Dehydration ...... 35

4.2. The Functionalization of the Cyclopentanone Ring ...... 39

4.3. First Dehydration ...... 41

4.4. Second Dehydration and the End Game...... 44

Chapter 5. Experimental Section ...... 49

Bibliography ...... 93

Appendix: 1H NMR Spectra ...... 98

LIST OF SCHEMES

Scheme Page

1.1 The Biosythetic Pathway of Fomannosin ...... 3

1.2 Matsumoto's Synthesis of the Fomannosin Skeleton ...... 5

1.3 Kasugi and Uda's Synthesis of (±)-5,6-Fomannosin Acetate ...... 7

1.4 Semmelhack's Total Synthesis of (±)-Fomannosin ...... 8

1.5 Retrosynthetic Analysis of Fomannosin ...... 10

2.1 Synthesis of 16...... 12

2.2 Synthesis of Vinylated furanosides 20 and 21...... 13

2.3 Synthesis of Vinylated furanosides 20 and 26...... 15

2.4 Zirconocene-mediated Ring Contraction Reaction ...... 16

2.5 Transition States for Zirconocene-mediated Ring Contraction ...... 17

2.6 Assembly of the Cyclopentene Ring ...... 19

3.1 The Cascade Michael Addition - Intramolecular Horner-Wadsworth-

Emmons Reaction Strategy ...... 22

3.2 Preparation of Fragments 36 and 39 ...... 23

3.3 Initial Attempts to Access 35 ...... 24

3.4 Attempted Michael addition - intramolecular Horner-Wadsworth-

Emmons Cascade Reaction ...... 25

3.5 Intramolecular Knoevenagel Condensation Strategy...... 26

3.6 Preparation of Monoallyl Malonic Acid 44 ...... 27

3.7 Knoevenagel Condensation of Monoallyl Malonic Ester 45...... 28

3.8 Preparation of the PMP Acetal 50 and its Allyl Deprotection...... 30

3.9 Attempts to Transform Allyl Ester 50 into Acid Chloride or Thioester 53.

...... 31

3.10 Reduction of Thioester 56...... 32

3.11 Formation of Enol 58...... 33

3.12 The Reduction of Enol 58 ...... 34

4.1 PMB Deprotection ...... 36

4.2 Attempted Dehydration of 64 ...... 37

4.3 Second Dehydration on 67 ...... 38

4.4 Attempted Hydroboration ...... 39

4.5 Functionization of the Cyclopentene ...... 40

4.6 First Dehydration ...... 42

4.7 Preparation of 77 and 78 from 62 ...... 43

4.8 Total Synthesis of Fomannosin (1) ...... 45

xii

LIST OF FIGURES

Figure Page

1 Fomannosin and Its Derivatives ...... 2

xiii

LIST OF TABLES

Table Page

1 Comparison of 1H NMR Data for Synthetic and Natural Fomannosin. . 47

2 Comparison of 13C NMR Data for Synthetic and Natural Fomannosin. .48

xiv

LIST OF ABBREVIATIONS

α alpha

[α] specific rotation

Ac acetyl

br broad (IR and NMR)

β beta

n-Bu normal-butyl

t-Bu tert-butyl

Bz benzoyl

°C degrees Celsius

calcd calculated

COSY correlation spectroscopy

CSA (1S)-(+)-10-camphorsulfonic acid

δ chemical shift in parts per million downfield from tetramethylsilane d doublet (spectra); day(s)

DBU 1,8-diazabicyclo[5.4.0]undec-7-ene

DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

DIBAL-H diisobutylaluminum hydride

xv DMAP 4-(N,N-dimethylamino)pyridine

DMF N,N-dimethylformamide

DMSO dimethylsulfoxide

EDCI 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride eq. equivalent

Et ethyl

γ gamma g gram(s) h hour(s)

HMBC heteronuclear multiple bond correlation

HMPA hexamethylphosphoramide

HRMS high resolution mass spectrometry

HSQC heteronuclear single quantum coherence

Hz hertz

IBX o-iodoxybenzoic acid imid. imidazole

IR infrared

J coupling constant in Hz (NMR) k kilo

KHMDS potassium hexamethyldisilazide

L liter(s)

LDA lithium diisopropylamide m milli; multiplet (NMR)

xvi µ micro

M moles per liter

Me methyl

MHz megahertz min minute(s) mol mole(s)

Ms methanesulfonyl

MS mass spectrometry; molecular sieves m/z mass to charge ratio (MS)

NaHMDS sodium hexamethyldisilazide

NMO 4-methylmorpholine N-oxide

NMR nuclear magnetic reasonance

NOE nuclear Overhauser effect (NMR)

NOESY nuclear Overhauser and exchange spectroscopy (NMR)

p para

Ph phenyl

PDC pyridinium dichromate

PMB p-methoxybenzyl

PMP p-methoxyphenyl ppm parts per million

PTSA p-toluenesulfonic acid pyr pyridine q quartet (NMR)

xvii Rochelle's salt potassium sodium tartrate

rt room temperature s singlet (NMR); second(s) t tertiary (tert) t triplet (NMR)

TBAF tetrabutylammonium fluoride

TBS t-butyldimethylsilyl

Tf trifluoromethanesulfonyl

TFA trifluoroacetic acid

THF tetrahydrofuran

TLC thin layer chromatography

xviii

CHAPTER 1

INTRODUCTION

1.1. Isolation, Biological Activity, and Structure Determination

Fomannosin (1) is a biologically active sesquiterpene metabolite first isolated in

1967 by Bassett and co-workers from the medium of the still culture of the wood-rotting fungus Fomes annosus (Fr.) Karst.1 F. annosus is one of the few wood-destroying

Basidiomycetes that affect pine stands in the southeastern United States. It was found that

F. annosus causes the death of the host cells prior to hyphal invasion,2 which suggested that phytotoxic metabolites produced by F. annosus might be responsible for killing the host cells. Indeed, no fomannosin was detected in naturally infected sapwood. However, after a still culture of F. annosus was grown in the dark for at least six weeks,1 fomannosin can be isolated from the chloroform extract of the culture medium.

Fomannosin was also isolated from Fomitopsis insularis.3 Fomannosin was found to be toxic toward 2-year-old pinus tadae seedlings, Chlorella pyrenoidose, and certain bacteria.1

Initially, the structure of fomannosin was partially elucidated by IR, UV and 1H

NMR spectroscopic studies.4 As fomannosin is unstable, all attempts for a satisfactory 1 elemental analysis or crystallographic study were unsuccessful. Fortunately, 5,6- dihydrofomannosin (2) could be easily prepared by catalytic hydrogenation of the natural product,4, 5a and was stable enough for crystallographic studies. The X-ray crystallographic analysis of the p-bromobenzoylurethane derivative (3) unambiguously revealed the structure of 3 and the relative stereochemistry.4 This also led to the postulation of the structure 1 as fomannosin since there is only one position to place the missing double bond. While this data is suggestive for the proposed structure of 1, the last piece of the fomannosin structural puzzle, its 7S, 9R absolute configuration, was established by a second X-ray study on the (-)-camphanate ester (4) of 5,6- dihydrofomannosin. 6

12 H H O 10 O 9 6 8 O O 3 5 4 2 O O 1 OH OR 1 2 R = H 3 R = p-Br-C6H4CONHCO 4 R = (-)-camphanyl

Figure 1 Fomannosin and Its Derivatives

1.2. Biosynthetic Studies

On the basis of double 13C-labeling experiments, a biosynthetic pathway for fomannosin has been proposed (Scheme 1.1).5 Biogenetically, mevalonate (5) is

2 converted to humulene (7) via intramolecular cyclization of trans-trans-farnisyl pyrophosphate. Further cyclization to a tricyclic compound 8 related to illudol was followed by oxidative cleavage of the appropriate bonds to yield fomannosin (1).

O P O HO 7 2

CH3CO2Na O O

5 6 7

H O

OH 8 1

Scheme 1.1 The Biosythetic Pathway of Fomannosin.

1.3. Synthetic Studies on Fomannosin: A Literature Review

Fomannosin represents a considerable challenge to synthetic chemists due to the inherent instability associated with its highly strained methylenecyclobutene unit and the reactive doubly unsaturated lactone ring. Not surprisingly, fomannosin is very sensitive toward both acid and base and prone to polymerization.7b In fact, it deteriorates over a few hours at 25 oC in deuterochloroform, forming an insoluble film on the NMR tube.7b

The challenging structure of fomannosin made fomannosin and its derivatives very interesting targets for total synthesis. Matsumoto and co-workers were the first to report a 3 synthesis of the fomannosin skeleton (Scheme 1.2).8 Starting with trans-1,2-dibromo-4,4-

dimethylcyclopentane, they placed the cyclopentanone unit in position by a series of straightforward transformations. The cyclobutane ring was assembled through a photochemical [2 + 2] cycloaddition with ethylene. The ketone group in the cyclopentanone unit was elaborated to the lactone through a Baeyer-Villiger oxidation.

After a few functional group modifications, an intramolecular Knoevenagel condensation was employed to construct the unsaturated lactone ring and furnish the fomannosin skeleton. The fact that the three cyclic units were assembled one after another provides valuable insight for the development of future synthetic strategies. However, this route has some obvious drawbacks. The synthetic route is racemic, and the end product was not adequately functionalized for the introduction of the C5/C6 double bond. In addition, the

[2 + 2] cycloaddition proceeded with low diastereoselectivity as the smallest olefin, ethylene, was used as a cycloaddition partner.

4 O O H H H Br 7 steps CH2=CH2, hv

Br H 62% cis-anti-cis AcO 24% cis-syn-cis H AcO

H O O O o 1) NaAl(OCH2CH2OMe)2H2 CH3CO3H, 25 C H O H 2) acetone, PTSA 50% H quant. yield OAc HO

O 1) Ag2CO3, xylene H 2) Morpholine, PTSA O H 6N HCl, 96% HO 3) O2, hv OH 4) NaBH4, EtOH HO 57% over 4 steps OH

1) MeO2CCH2COCl, H H Pyr., 72% O O O PhH/Pyr., reflux O 2) Jones oxidation, O OMe 36% O 68% O O CO2Me

Scheme 1.2 Matsumoto's Synthesis of the Fomannosin Skeleton

5 Kosugi and Uda reported their approach to (±)-5,6-fomannosin acetate in 1977

(Scheme 1.3).9 Similar to Matsumoto's route, the cyclobutane was constructed through a

[2+2] photochemical cycloaddition of ethylene to the key butenolide intermediate. The cyclobutane-fused lactone was then further elaborated to introduce the -keto ester, followed by introduction of the C1 hydroxyl group and C2/C4 double bond. It was also found that attempts to obtain 5,6-dihydrofomannosin through the saponification of (±)-

5,6-fomannosin acetate were not successful. The major drawback of this route is the lack of stereodiscrimination at C7 and C9 during the formation of the cyclobutane. As in

Matsumoto’s work (vide infra), this approach does not allow for further modification to introduce the C5/C6 double bond.

6 O 1) LDA 1) NaBH4, MeOH H H + S AcO 2) Heat O 2) Ac2O, Pyr. O O O O 54% O 82% O O

S H 1) MeS , BuLi H AcO S AcO CH2=CH2, hv 85% 2) Ac O, Py OAc O 2 3) HgCl2, HgO, EtOH CO2Et 74% O O

H 1) KOH H AcO 2) PTSA, PhH THPO 1) OsO4, Pyr. 1) Ph3P=CH2 reflux OAc O 2) Ac2O, Pyr. 2) Separation 3) dihydrofuran, CO Et 33% 2 PTSA O 92%

H H H THPO HO O 1) MsCl, Et3N CrO3, H2SO4, O O O 2) LiCl, Li2CO3, acetone o O DMF, 110-160 C; O 20% over 3 steps O then diluted H SO HO OAc 2 4 OAc OAc

Scheme 1.3 Kasugi and Uda's Synthesis of (±)-5,6-Fomannosin Acetate

In 1981, Semmelhack reported the first total synthesis of (±)-fomannosin, which was innovatively based on the insight into the possible biosynthetic relationship between illudol10, 11 and fomannosin (Scheme 1.4).7 In this route, the Diels-Alder reaction of a cyclobutenecarboxylate with an appropriate diene was used to stereospecifically generate

7 a tricyclic protoilludane skeleton. A subsequent Baeyer-Villiger oxidation set up the functionalization of the cyclopentanone. The C1 hydroxylmethyl group and C2/C4 double bond were installed by formylation of the lactone followed by selenoxide elimination. Simultaneous elimination of a mesylate and desilylation effected by tetrabutylammonium fluoride completed the first total synthesis of (±)-fomannosin.

OTMS OTMS

CO2Me CO2Me EtO OEt o DCM, 50 C H + OEt o 65% 48 C, 10d, 72% OEt H CO2Me EtO OEt

1) HCl, acetone O H O H 1) LiAlH4 O 2) TBSCl, imidazole O

2) 3 A sieves, MeOH 3) NaBH4 1) LDA, CH2O H H 3) mCPBA H 4) dihydrofuran, PTSA H 2) LDA, PhSeCl 90% OH 74-77% OTBS 47% EtO OEt OTHP

O H O H O O PhSe HO 1) CH2=CHOEt, PTSA PPTS, MeOH, then H2O2 2) MsCl, Et3N HO H 3) 48% HF, CH CN H 71% H 3 OTBS OTBS 58% OTHP OH

O O OH TBSO OH O O O OH O O O 1) TBSCl, imidazole TBAF, THF, 22 oC . 2) CrO3 Py H H 81% H OMs 86% OMs

Scheme 1.4 Semmelhack's Total Synthesis of (±)-Fomannosin 8 1.4. Retrosynthetic Analysis

Due to its highly strained methylenecyclobutene unit, great care must be taken to install one or both of fomannosin’s double bonds at the final stage of the synthesis

(Scheme 1.5). With this in mind, it was believed that the C5/C6 double bond should be masked as a protected hydroxyl group as in 9. The C1 hydroxyl group could be derived from the reduction of a carbonyl functionality. The ,-unsaturated lactone ring in 9 would be constructed through the formation of the C2/C4 double bond, which could potentially be realized by attaching a functionalized side chain to intermediate 10 through esterification and fusing the ring system by ring-closing metathesis or intramolecular

Knoevenagel condensation. The cyclopentanone subunit in 10 was envisioned to be derived from the vinyl group in 11. There are several options for this transformation, including a [2+2] cycloaddition of a suitably reactive ketene to 11 followed by ring expansion, a McMurry or related pinacol coupling of an appropriate dicarbonyl precursor, or a ring-closing metathesis of a suitably substituted diene generated from 11.

The cyclobutane 11, which features three contiguous stereogenic centers along the periphery of its four-membered ring, could be generated stereoselectively through a zirconocene-mediated ring contraction reaction of vinylated furanoside 12.12, 13 In turn,

12 could be derived from D-glucose.

9 12 H H H O 10 O O 9 6 8 O O OR' 3 RO O 5 4 2 O RO OR" 1 OH X O X = H, OAll, or SEt 1 9 10

R'O OH O OCH3 O OR' HO HO RO OR" OH OH OR"

11 12 D-Glucose

Scheme 1.5 Retrosynthetic Analysis of Fomannosin

This project was initiated by Dr. Ho-Jung Kang and further advanced by Dr. Jiong

Yang, who developed a viable route to cyclopentanone 10.15 To provide a global view of this project, their cumulative work that has been adopted in the final synthetic route leading to (+)-fomannosin will be discussed in Chapter 2.

CHAPTER 2

CONSTRUCTION OF THE CYCLOBUTANE AND CYCLOPENTANONE RINGS

2.1. Synthesis of the Ring-Contraction Precursor: Vinylated Furanosides.

Synthesis of fommanosin commenced with D-glucose, which was easily

transformed in two steps to known tosylate 13 (Scheme 2.1).16 Selective acetonide hydrolysis in 13 was effected with diluted surfuric acid in methanol 17 to generate a vicinal diol, whose glycolic C-C bond was oxidatively cleaved with sodium periodate.

The resulting aldehyde was further oxidized to the corresponding carboxylic acid under

Lindgren conditions and quantitatively transformed into its methyl ester 14 with diazomethane.18 Deoxygenation at the C3 position was achieved through a two-step reaction sequence. The tosylate of 14 was eliminated using DBU and the resulting enoate was hydrogenated over a catalytic amount of Pd/C to afford 15 as a single diastereomer.

The hydrogen occurred preferentially on the face as a result of the steric bulk imparted by the acetonide. This five-step reaction sequence from 13 to 15 proceeded with remarkable efficiency (90%) without the need for column chromatography or recrystallization. Hydrolysis of the residual acetonide 15 with HCl in hot methanol and subsequent exposure of the product to PMB protection with p-methoxybenzyl 11 trichloroacetimidate19 afforded a 3.5:1 mixture of anomers 16 and 17 in 88% combined yield. On large scale, the purification of 16 was difficult and time-consuming. Even after repeated chromatographic purification, the product was always contaminated with the byproduct CCl3CONH2, which in turn had deleterious effects on the next reaction. This problem was solved by dissolving the crude product in hexane with the aid of a small amount of dichloromethane. This operation results in almost quantitative precipitation of

CCl3CONH2. The minor anomer 17 could be readily recycled to 16 by equilibration at 55

°C in a mixture of methanol and trimethyl orthoformate containing catalytic amounts of

HCl.

OH O 1) H2SO4, CuSO4, 1) H2SO4, CH3OH O acetone, 52% O HO O 2) NaIO4, THF/H2O HO OTs 2) TsCl, Et N, OH OH 3 O DMAP, 83% 3) NaClO2; CH2N2 O D-Glucose 13

1) HCl, CH3OH O 1) DBU, CH2Cl2 NH H3CO2C O OTs 2) 10% Pd/C, H2 H CO C O 3 2 2) PMBO CCl3 , CSA O O O 90% over 5 steps 88%, 1β/1α = 3.5/1 15 14

O OCH3 O + H3CO2C H3CO2C OCH3 OPMB PMBO

16 17

+ (MeO)3CH, MeOH, H

Scheme 2.1 Synthesis of 16 12 Elaboration of the C4 position started with alkylation of the lithium enolate of 16

with monomeric formaldehyde;20 an excess must be used to guarantee high yield. The diastereomeric alcohol intermediates resulting from alkylation were separated by column chromatography in a ratio of 1.7:1. After the newly produced hydroxyl groups were protected as the tert-butyldiphenylsilyl ethers, diastereoisomers 18 and 19 were obtained respectively (Scheme 2.2). Following DIBAL-H reduction of the ester and Swern oxidation to the aldehyde, Wittig olefination produced vinylated furanosides 20 and 21, which have set the stage for the zirconocene-mediated ring contraction reaction.

However, the route delineated in Scheme 2.2 generated diastereomers at both the acetonide hydrolysis and prior alkylation step, and separating them chromatographically proved to be very time-consuming.

TBDPSO 1) DIBAL-H TBDPSO OCH OCH O 3 2) Swern oxidation O 3

H3CO2C 3) Ph3P=CH2 OPMB OPMB 79% over 3 steps 18 20

1) LDA, CH2O 2) TBDPSCl, im. 16 86%, β/α =1.7/1

1) DIBAL-H OCH H CO C OCH O 3 3 2 O 3 2) Swern oxidation

3) Ph3P=CH2 TBDPSO TBDPSO OPMB OPMB 74% over 3 steps 19 21

Scheme 2.2 Synthesis of Vinylated furanosides 20 and 21

13 Consequently, the hydroxymethylation was performed on 15 to take advantage of

the steric screening provided by the acetonide in controlling the approach of the monomeric formaldehyde from the face of the enolate exclusively (Scheme 2.3). As expected, 22 was produced as a single diasteromer in 50% yield over 2 steps. Sequential partial reduction with DIBAL-H and Wittig olefination of 22 to afford 23 proceeded uneventfully. The one-pot deprotection of the acetonide and glycosidation with HCl in methanol afforded separable anomers 24 and 25 in 73% combined yield. Protection of the exposed C2 hydroxyl groups as p-methoxybenzyl ethers delivered the epimeric methyl glycosides 20 and 26.

14 O TBDPSO O 1) LDA, CH2O, 52% 1) DIBAL-H, DCM H CO C O 3 2 2) TBDPSCl, imid., 93% 2) Ph P=CH O H3CO2C O 3 2 O 81% over 2 steps

15 22

TBDPSO TBDPSO TBDPSO O O OMe O conc. HCl O + OMe CH3OH O OH OH

23 24 (43%) 25 (30%)

PMBBr, PMBBr, NaH, DMF, NaH, DMF, rt, 85% rt, 82%

TBDPSO TBDPSO O OMe O

OMe OPMB OPMB 20 26

Scheme 2.3 Synthesis of Vinylated furanosides 20 and 26

2.2. The Zirconocene-mediated Ring Contraction Reaction

While there have been several successful examples featuring vinylated furanosides as substrates,12, 13, 14 compounds 20, 21 and 26 represent a new class of vinylated furanoside substrates where a quaternary chiral center on the cyclobutane will be generated after the zirconocene-mediated ring contraction. This proved not to be a great concern as long as the zirconocene dichloride was purified by sublimation prior to use.

15 21 Under fine-tuned ring contraction conditions, controlled exposure of 20 to “Cp2Zr” gave rise to a diastereomeric mixture of 27 and 28 (~1.7:1) in up to 84% yield (Scheme

2.4). Fortunately, the desired product 27 is the major product. Exposure of 21 to the same zirconocene-mediated ring contraction conditions gave similar results. However, there was no reaction when the -anomer 26 was treated with “Cp2Zr”.

TBDPSO O OCH3

OPMB 20 Cp2ZrCl2, BuLi OTBDPS OTBDPS + or o -78 C → rt PMBO OH PMBO OH O OCH3 70-84% 27/28 ~ 1.7/1 27 28 TBDPSO OPMB 21

Scheme 2.4 Zirconocene-mediated Ring Contraction Reaction

To rationalize the product distribution, the ring closure transition states must be considered. Initial coordination of the zirconocene to the olefin and furanoside oxygen ensures E geometry for the developing allylzirconium intermediate. Opening of the furanoside to the chelated aldehyde can proceed via transition states A and B. Ring closure through transition state A will give rise to 27, while transition state B leads to 28.

Presumably, the adoption of B is less favored as a consequence of nonbonded steric interactions between the methylene group of the developing cyclobutane and the allylic methylene group to the zirconium. Thus, 28 was obtained as the minor product. The fact that C4-epimer 21 gave similar yield and product distribution is consistent with the 16 proposed mechanistic pathway in which A and B are again involved in the formation of

the cyclobutanols.

TBDPSO TBDPSO OCH O OCH3 O 3 Cp2Zr OPMB OPMB ZrCp2 20

H H H Cp H Cp + + Zr O Zr H O Cp PMBO PMBO Cp H H H OTBDPS OTBDPS A B

OTBDPS OTBDPS

PMBO OH PMBO OH

27 28

Scheme 2.5 Transition States for Zirconocene-mediated Ring Contraction

2.3. Assembly of the Cyclopentene Ring

With cyclobutanol 27 in hand, assembly of the cyclopentanone commenced

(Scheme 2.6). The vinyl group in 27 was designed to serve as the bridge to the cyclopentanone unit in fomannosin (1). Three possible convergent strategies to this challenge have been investigated. The first involved [2+2] cycloaddition of

17 dichloroketene with derivatives of 27,22 followed by one-carbon ring expansion of the resulting cyclobutanone. The next strategy called upon the McMurry reaction23 or related pinacol couplings24 for assembly of the cyclopentanone subunit. Both strategies turned out to be of no avail.

Recourse was then made to ring-closing metathesis25 to first construct a cyclopentene ring. To this end, cyclobutanol 27 was protected as its TBS ether. The double bond was cleaved by ozonolysis with Sudan III as the internal indicator26 to provide aldehyde 29, which was alkylated in near quantitative yield with the lithium reagent generated through the lithium-halogen exchange reaction27 between 5-iodo-4,4-dimethylpent-1-ene and t- butyllithium. Oxidation of the resulting carbinol 30 with PDC afforded ketone 31 in 83% yield. Methylenation of the sterically congested ketone 31 was problematic, as conventional methylenation reagents such as Wittig,28 Tebbe,29 and Nysted30 reagents proved to be ineffective. This conversion was finally accomplished by resorting to

Peterson olefination31 to generate diene 32. The cyclopentene ring was formed by ring- closing metathesis using Grubbs 2nd generation catalyst32 to deliver 33 in 91% yield.

18 CHO I OTBDPS 1) TBSCl, imid., 91% OTBDPS t-BuLi, THF, -78 oC

PMBO OH 2) O3, Sudan III, CH2Cl2; PMBO OTBS 96%

then, PPh3, 91% 27 29

1) TMSCH2Li, HO PDC, 4 Å MS O pentane/toluene

OTBDPS CH2Cl2, rt, 24 h OTBDPS 2) PTSA, PhH 83% 83% PMBO OTBS PMBO OTBS

30 31

Mes N N Mes Grubbs-2 Cl OTBDPS OTBDPS Ru PhH, reflux. Cl Ph PCy PMBO OTBS 91% PMBO OTBS 3 Grubbs-2 32 33

Scheme 2.6 Assembly of the Cyclopentene Ring

CHAPTER 3

ASSEMBLY OF THE LACTONE UNIT

3.1 The Michael Addition - Intramolecular Horner-Wadsworth-Emmons Cascade

Reaction Approach

In Chapter 2, a facile route utilizing a zirconocene-mediated ring contraction reaction to access cyclopentene 33 was disclosed. With 33 in hand, installation of the C13 carbonyl group through a hydroboration-oxidation approach appeared to be a natural choice. However, it was soon discovered that 33 was very slow to react even with more reactive hydroborating reagents such as the borane-tetrahydrofuran or borane-dimethyl sulfide complexes.15 Neither elevated temperatures nor prolonged reaction times resulted in complete conversion. In addition, the desired product was isolated as a pair of inseparable diastereomeric alcohols in relatively low yield.

At this point, it was believed that installation of the C13 carbonyl group should be delayed until formation of the lactone ring was completed. In this manner, the carbonyl group would not interfere with lactone formation or introduction of the hydroxymethyl group at the C1 position. Furthermore, removal of the bulky TBS and TBDPS protection groups should facilitate the hydroboration of the trisubstituted cyclopentene double bond. 20 Preliminary results by Dr. Jiong Yang showed that applying a ring-closing metathesis strategy to anneal the lactone at the site of the tetrasubstituted C2-C4 double bond would not be successful,15 as the precursor for ring-closing metathesis could not be accessed.

An attractive alternative was to form the tetrasubstituted C2-C4 double bond through a Michael addition - intramolecular Horner-Wadsworth-Emmons reaction cascade33, 34 (Scheme 3.1). The Michael addition of a nucleophilic alkoxide, such as p- methoxybenzyl alkoxide, to the Michael acceptor 35 would result in a stabilized anion, which would undergo intramolecular Horner-Wadsworth-Emmons reaction with the cyclobutanone to deliver the unsaturated lactone 34. The Michael addition and -

elimination of the ylide would be in equilibrium. However, the ensuing intramolecular

Horner-Wadsworth-Emmons reaction would serve to shift the equilibrium in favor of the formation of 34. This approach held the advantage that the generation of C2-C4 double bond would be facilitated by elimination of the phosphonic acid. The C1 position would also be installed with the correct oxidation state simultaneously.

21 H O

O O

O PMBO O OH OPMB

1 34

O O O O P(OEt)2 O OTBDPS P(OEt) + HO 2 PMBO O PMBO OTBS O PMB

35 33 36

Scheme 3.1 The Cascade Michael Addition - Intramolecular Horner-Wadsworth- Emmons Reaction Strategy

Known phosphonate 36, which corresponds to the C1-C3 segment in 1, was prepared

in three steps (Scheme 3.2).35a The fact that Michael addition of p-methoxybenzyl alcohol to 37 proceeded in nearly quantitative yield at room temperature35 implied that 35 would likely be an excellent Michael acceptor.

22 O O O O 1) (C6H11)2NH PMBOH,PhH (C6H11)2H2N O2C P(OEt)2 P(OEt) (C H ) H N O C P(OEt) 2 6 11 2 2 2 2 rt HO 2) (CH2O)n, Et3N, PhH, reflux OPMB 38% 38 37

aq. HCl, aq. HCl, 100% 93% over 2 steps

O O

HO2C P(OEt)2 HO2C P(OEt)2

OPMB 36 39

Scheme 3.2 Preparation of Fragments 36 and 39

To prepare the cascade reaction precursor 35, the TBDPS ether in 33 was selectively removed in the presence of TBS ether with a mixture of TBAF and HOAc to afford 40 in

78% yield (Scheme 3.3).36 The coupling of 40 with fragment 36 promoted by EDCI proceeded smoothly to provide 41 in 75% yield.37 However, the ensuing TBS deprotection using HF-Pyridine38 gave a complex mixture.

23 O HO2C P(OEt)2 TBAF, HOAc, 36 OTBDPS THF, rt; 78% OH EDCI, DCM; 75% PMBO OTBS PMBO OTBS

33 40

O O O O HF-Pyr, THF P(OEt)2 P(OEt)2 O O PMBO OH PMBO OTBS

42 41

Scheme 3.3 Initial Attempts to Access 35

To circumvent this problem, the TBDPS and TBS ethers of 33 were removed

simultaneously with an excess of TBAF to provide diol 43 in 76% yield (Scheme 3.4).

Under carefully controlled reaction conditions, the primary hydroxyl group of diol 43 was selectively esterified with fragment 36 to deliver 42 in 82% yield. The secondary hydroxyl group in 42 was easily oxidized with IBX39 to afford ketone 35 in 55% yield, which was ready for the cascade Michael addition - intramolecular Horner-Wadsworth-

Emmons reaction. The cascade reaction was attempted both with PMB alcohol in the presence of cesium carbonate and with PMB alkoxide (prepared in situ by premixing

PMB alcohol with sodium hydride). Unfortunately, both conditions resulted in the decomposition of 35.

24 O HO2C P(OEt)2 O O TBAF, THF 36 P(OEt) OH O 2 OTBDPS 76% EDCI, DCM; 82% PMBO OTBS PMBO OH PMBO OH

33 43 42

O O PMBOH, Cs CO IBX, DMSO P(OEt) 2 3 O 2 O 55% or PMBO O PMBOH, NaH PMBO O OPMB 35 34

Scheme 3.4 Attempted Michael addition - intramolecular Horner-Wadsworth-Emmons Cascade Reaction

Ketone 35 proved to be very capricious and difficult to handle. It gradually decomposed during column chromatographic purification and upon storing at 0 oC.

Efforts towards installation of the lactone via cascade Michael addition - intramolecular

Horner-Wadsworth-Emmons reaction were abandoned.

25 3.2 The Intramolecular Knoevenagel Condensation Strategy

3.2.1 Knoevenagel Condensation with Monoallyl Malonic Acid

Attention was directed to implementation of an intramolecular Knoevenagel condensation40 to construct the unsaturated lactone ring (Scheme 3.5). Intramolecular

Knoevenagel reaction of -ketoester 45 would lead to lactone 46. The selective reduction of the carboxylic acid resulting from allyl deprotection of 46 would put the C1 hydroxylmethyl group into position. The Knoevenagel condensation precursor 45 could be derived from the coupling of 43 and fragment 44, following an analogous approach to the formation of 35.

H O Knoevenagel O O Condensation O O O OAll

O PMBO O PMBO O CO2All OH 1 46 45

O O OH + HO OAll PMBO OH

43 44

Scheme 3.5 Intramolecular Knoevenagel Condensation Strategy

26 Monoallyl malonic acid 44 was easily prepared in quantitative yield by treating

Meldrum’s acid 47 with allyl alcohol in benzene at reflux (Scheme 3.6).41

O O O O Allyl alcohol, PhH HO OAll O O reflux; 100% 47 44

Scheme 3.6 Preparation of Monoallyl Malonic Acid 44

Surprisingly, the coupling of diol 43 with fragment 44 turned out to be far from trivial (Scheme 3.7). A mixture of inseparable mono & diacylated products, 47 and 48, was obtained. Even with fragment 44 as the limiting reagent, the desired product 47 was always contaminated with about 10% of 48. Fortunately, when the mixture was treated with IBX, the unreacted compound 48 could be easily removed by column chromatography. Under chromatographic conditions, half of the oxidation product 45 cyclized spontaneously to give 49. Compounds 45 and 49 seemed to be in equilibrium and a 1:1 mixture was always obtained despite repeated column chromatographic purification. The effort to convert 45 completely to 49 to regain chemical homogeneity was fruitless. When a mixture of 45 and 49 was treated with DBU in benzene, no conversion was observed at room temperature. When the reaction mixture was brought to reflux, the cyclobutane ring was destroyed. When a mixture of 45 and 49 was stirred with either silica gel in dichloromethane or with PTSA in tetrahydrofuran, no reaction could be detected and the mixture of 45 and 49 was recovered in both cases. The mixture of 45

42 and 49 was then subjected to dehydration conditions with MsCl and Et3N catalyzed by

27 DMAP (Scheme 3.7). Although large excesses of MsCl and Et3N were added, the reaction failed to provide complete conversion. Unsaturated lactone 46 was separated from the reaction mixture; however, with the introduction of the angular double bond, 46 was not stable.

O O O O O O HO OAll OH 44 O OAll + O OAll O EDCI, CH Cl , 74% O PMBO OH 2 2 PMBO OH PMBO O OAll

43 47 48 (~ 10%)

O O IBX, DMSO; O O OAll Silica gel; + PMBO O 74% combined PMBO O HO CO2All

45 49

MsCl, Et3N, DMAP, CH2Cl2 23% (58% based on rec. of SM)

PMBO O CO2All

Scheme 3.7 Knoevenagel Condensation of Monoallyl Malonic Ester 45

28 Since the dehydration product 46 was unstable, an obvious alternative approach was to reduce the allyl ester prior to the generation of the C2-C4 double bond. Without the electron-withdrawing allyl ester, the dehydration product was expected to have increased stability.

To this end, the inseparable mixture of 45 and 49 (~ 1:1) was treated with DDQ in the presence of 4Å molecular sieves (Scheme 3.8).43 The pure PMP acetal 50 was successfully obtained as a single diastereomer in 52% yield and fully characterized. The configuration of C2, C4 and the PMP acetal was established based on NOE correlations

44 from NOESY experiments. When 50 was treated with Pd(PPh3)4 and morpholine, the protecting group removal and decarboxylation happened spontaneously to afford 51.

When an acidic allyl scavenger, dimedone,45 was used instead of the basic morpholine,

46 the decarboxylation product 51 still prevailed. The combination of NaBH4 and I2 was utilized to attempt deprotection of the allyl group and reduction of the resulting carboxylic acid in one pot, which failed to give the desired product as all the material stayed at the baseline on the TLC plate.

29 O O o DDQ, 4A MS O O OAll + DCM, 52% O PMBO O PMBO HO CO2All

45 49

Pd(PPh ) , morpholine, O 3 4 O H THF, 65% H O H O O O O O CO2All PMP PMP

50 51

Scheme 3.8 Preparation of the PMP Acetal 50 and its Allyl Deprotection

The combination of PhSiH3 and Pd(PPh3)4, a very mild and neutral allyl ester deprotection method,47 was also investigated. It provided the silyl ester 52 as a reactive intermediate. However, all attempts to transform 52 directly into the acid chloride

48 ((COCl)2, DMF, DCM) or thioester (PhSH, THF) resulted only in decomposition of the starting material 50.

30 (COCl)2, DMF, O Pd(PPh3)4, PhSiH3 O CH Cl , rt O H H 2 2 H H O CH2Cl2 H O or H O O O O O O O CO2All CO2SiH2Ph PhSH, THF COX PMP PMP PMP X = Cl or SPh 50 52 53

Scheme 3.9 Attempts to Transform Allyl Ester 50 into Acid Chloride or Thioester 53

3.2.2 Knoevenagel Condensation with Ethylsulfanylcarbonyl Acetic Acid

The transformation of the allyl ester to the desired C1 hydroxymethyl group proved

to be insurmountable. Replacing the allyl ester with an activated carbonyl functionality, such as a thioester, which could be selectively reduced in the presence of the labile lactone, appeared to be a suitable alternative.

To this end, recourse was made to couple diol 43 with ethylsulfanylacetic acid49

(Scheme 3.10). Following the same protocol developed for allylmalonate, an inseparable mixture of ketone 54 and its cyclized form 55 was obtained after IBX oxidation. The mixture was treated with DDQ in the presence of 4Å molecular sieves to afford PMP acetal 56 in an unoptimized yield (26%). The direct reduction of thioester 56 to the

50 corresponding alcohol was not successful. When NaBH4 in ethanol was used, the labile lactone was cleaved. Attempts to transform the thioester into aldehyde 57 resulted in no

51 reaction using either Pd/C or Pd(OAc)2 in the presence of Et3SiH in acetone, which was quite surprising.

1. HO2C COSEt

EDCI, CH2Cl2 O O OH + O 2. IBX, DMSO O SEt O PMBO OH 44% over 2 steps PMBO HO PMBO O COSEt

43 54 55

Pd/C, Et3SiH, DDQ, 4Å MS O acetone O

CH2Cl2, 26% O or O O O Pd(OAc) , Et SiH O O COSEt 2 3 CHO acetone PMP PMP

56 57

Scheme 3.10 Reduction of Thioester 56

Likely, the steric hindrance around the thioester in 56 prevented the reducing agent from approaching the thioester. Similar steric congestion could be expected for cyclized compound 55. However, there must be substantially less steric hinderance around the thioester in the open chain compound 54. The partial reduction of the thioester in 54 might have a two-fold impact. It would facilitate the spontaneous ring closure since the resulting aldehyde ester would be more reactive for Knoevenagel condensation.

Furthermore, it would shift the equilibrium from 55 to 54. In fact, when a mixture of 54 and 55 was subjected to partial reduction with Pd/C and triethylsilane (Scheme 3.11),51 enol 58 was obtained in 76% yield after silica gel column chromatography. 1H NMR showed that 58 resided completely in its enol form. The further reduction of enol 58 with 32 52 53 NaBH(OAc)3 in acetic acid/acetonitrile or Me4NBH(OAc)3 in combination with CeCl3

54 resulted in decomposition of 58. No reaction was observed with LiAlH(O-t-Bu)3. When

NaBH4 in ethanol was used, the labile lactone was again cleaved to afford diol 43 in 58% yield.

O O + O Pd/C, Et3SiH,DCM; O SEt O Silica gel; 74% PMBO HO PMBO O COSEt

54 55

O NaBH4, EtOH OH 58% PMBO O HO PMBO OH OH 58 43

Scheme 3.11 Formation of Enol 58

The reduction of enol 58 was further pursued (Scheme 3.12). Finally, it was found

that in a mixture of methanol/acetonitrile, with careful control of the amount of NaBH4 added, both diastereomeric alcohols, 59 and 60 were obtained in 31% and 20% yield, respectively.55 A better result was obtained when the pH of the reduction media was kept neutral using sodium dihydrogen phosphate and glacial acetic acid. The primary hydroxyl groups in 59 and 60 were selectively protected56 as TBS ethers 61 and 62 respectively.

With the TBS ethers in place, the lactone was both isolable and fully functionalized.

33 * NaBH4, MeOH/CH3CN, 0 oC; (59, 31%; 60, 20%) O O + O * NaBH , MeOH, NaH PO , PMBO O 4 2 4 PMBO O PMBO O HO HOAc, 0 oC; HO HO OH (59, 37%; 60, 27%) OH OH 58 59 60

TBSOTf, TBSOTf, 2,6-lutidine, 2,6-lutidine, o o CH2Cl2, -78 C CH2Cl2, -78 C 89% 74%

O O

PMBO O O HO PMBO HO OTBS OTBS 61 62

Scheme 3.12 The Reduction of Enol 58.

CHAPTER 4

COMPLETION OF THE TOTAL SYNTHESIS

4.1 PMB Deprotection and Dehydration

With the acquisition of lactones 61 and 62, there were two major issues remaining to be resolved to complete the synthesis: A protocol was needed for installation of the cyclopentanone; and more daunting, a method for the introduction of the diene functionality by the dehydration of the C4 and C5 hydroxyl groups. We decided to take advantage of having both diastereomers 61 and 62 and pressed forward in both directions simultaneously.

For dehydration to be effective, the C5 hydroxyl group must first be exposed.

Deprotection of the PMB group proved to be far from trivial (Scheme 4.1). When 62 was treated with DDQ57 in a mixture of dichloromethane and pH 7 buffer, the benzylic position was oxidized to the benzoate57b to afford 63. An alternative deprotection procedure using cerium ammonium nitrate (CAN) in aqueous acetonitrile57a only resulted in deprotection of the TBS ether to give 60. The deprotection was finally achieved using

TFA under anhydrous conditions58 to deliver diol 64 in 72% yield.

35 DDQ,

CH2Cl2/pH 7 buffer 54% O O O HO MeO O OTBS

CAN,

CH3CN/H2O O 88% O O PMBO HO O PMBO HO OTBS OH 62 60

TFA, CH2Cl2; 72% O

O HO HO OTBS 64

Scheme 4.1 PMB Deprotection

Diol 64 was ready for double dehydration to provide 65. However, treatment of 64 with an excess amount of Martin sulfurane59 resulted in complete decomposition

(Scheme 4.2). It was realized that the dehydration should be performed in a stepwise fashion. To this end, 64 was treated with thionyl chloride in the presence of triethylamine to afford cyclic sulfite 6660 as an inconsequential pair of diastereomers. Cyclic sulfite 66

36 partially converted to 67 upon coming into contact with silica gel. The complete

conversion of 66 to 67 was accomplished by treatment with DBU in dichloromethane.60b

O Martin sulfurane O CH Cl O 2 2 O HO HO OTBS OTBS 64 65

SOCl2, Et3N, o CH2Cl2, 0 C

F3C CF3 O DBU, CH Cl , 0 oC Ph Ph 2 2 S O O Ph Ph 52% over 2 steps O O O F3C CF3 O O HO S Martin sulfurane OTBS OTBS O 66 67

Scheme 4.2 Attempted Dehydration of 64

As alcohol 67 was available and ready for the second dehydration to form the cyclobutene ring, the second dehydration was tested (Scheme 4.3). The combination of thionyl chloride and pyridine,61 resulted in no desirable reaction, albeit partial formation of the chlorosulfonyl ester. Recourse was made to form the mesylate 68 first,62 which was easily obtained in 83% yield. However, the simultaneous elimination and deprotection of the TBS ether with TBAF7 only resulted in the decomposition of the mesylate 68. Use of

37 the Martin sulfurane at 0 oC resulted in no reaction. But a trace amount of desired product

65 was obtained at room temperature contaminated with reagent byproducts, as supported by 1H NMR and HR-MS.

SOCl2, Pyr, O o CH2Cl2, 0 C OTBS 65

O MsCl, Et3N, CH2Cl2, O TBAF, THF O -30 oC, 83% HO O MsO O O OTBS OTBS OH 67 68 69

Martin sulfurane, CH2Cl2, rt

OTBS 65 (trace amount)

Scheme 4.3 Second Dehydration on 67

The road leading to alcohol 67 has established a viable protocol for the PMB deprotection and the first dehydration.

38 4.2 The Functionalization of the Cyclopentanone Ring

As planned, lactone 62 was subjected to hydroboration-oxidation63 to introduce the

C13 carbonyl group (Scheme 4.4). It was found that four compounds were produced from the reaction in near equal amounts as shown by 1H NMR and COSY spectra. Along with the desired addition products 70, the C4 hydroxyl group also directed the addition of borane to afford a pair of inseparable tertiary diols 71.15 Fortunately, the lactone ring remained intact when sodium perborate was used to oxidize the borane adduct.64 The complexity of this reaction did not warrant further investigation.

HO H OH . o BH3 THF, THF, 0 C; O O + O NaBO3, H2O O PMBO O O PMBO HO HO PMBO HO OTBS OTBS OTBS 62 70 71

Scheme 4.4 Attempted Hydroboration

Recourse was made to introduce the cyclopentanone functionality following the dihydroxylation, oxidation, and SmI2 mediated -deoxygenation strategy (Scheme 4.5).

Thus, lactone 61 was subjected to dihydroxylation with a stoichiometric amount of

65 OsO4 followed by quenching the reaction with an excess amount of H2S(g) to afford triol 72. Surprisingly, 72 was obtained as a single diastereomer. The secondary hydroxyl group was successfully oxidized by Swern Oxidation to deliver 73.66 A NOESY experiment on 73 showed that C9 containing the tertiary hydroxyl group was of the R-

39 configuration, which must have been a result of the directing effect of the C4 hydroxyl

group during the course of the dihydroxylation.

OH HO OsO4, THF/Pyr; (COCl)2, DMSO, O O H2S; 76% Et3N, CH2Cl2 O O PMBO HO PMBO HO 79% OTBS OTBS 61 72

OH H O O Conditions O O

O O PMBO HO PMBO HO OTBS OTBS 73 74

Conditons: yield of 74

SmI2, MeOH/THF 30%

SmI2, Ethylene glycol, 17% HMPA, THF

SmI2, t-BuOH/THF 64%

Scheme 4.5 Functionization of the Cyclopentene

Initially, the SmI2-mediated -deoxygenation of 73 was performed with 3.0

67 equivalent of SmI2 using methanol as the proton source, which provided 74 as a pair of inseparable diastereomers in 30% yield (Scheme 4.5). When ethylene glycol was used as

40 the proton source instead67b, the yield was worse, affording 74 in 17% yield based on recovery of the starting material. However, the reaction was greatly improved with t- butyl alcohol as the proton source;67c and cyclopentanone 74 was obtained in 64% yield.

4.3 First Dehydration

When fully functionalized compound 74 was subjected to deprotection of the PMB group with TFA in anhydrous dichloromethane, the reaction proceeded smoothly to afford two diastereomers 75 and 76, which were readily separated by column chromatography. The configurations of the C9 chiral centers of 75 and 76 were not immediately clear. Subsequent assignment of the configuration was possible upon arrival at the natural product. Although Kosugi and Uda mentioned in their synthesis of 5,6- dihydrofomannosin acetate9 that the configuration of the C9 chiral center could be assigned based on the chemical shift difference between the two C8 protons via 1H

NMR,8 it was not the case here, as the C5 and/or C4 hydroxyl groups interfered with the orientation of the cyclopentanone ring. In the case of 75, which has the C9 proton at the

position, the chemical shift difference between the two C8 protons is 1.12 ppm, whereas for 76, the chemical shift difference is 0.18 ppm. On a small scale with longer reaction time (>15) min at room temperature, the two diastereomers, 75 and 76, were isolated in a ratio of approximately 1:1. On a larger scale, the reaction was quenched after

8 min, which afforded the C9 -epimer 75 in only 8% yield. The desired -epimer was the major product (50%). Obviously, the C9 stereocenter epimerized rapidly under the acidic conditions. When 9 epimer 76 was subjected to dehydration, formation of the

41 cyclic sulfite proceeded uneventfully. However, under DBU elimination conditions, TLC

clearly showed that product 78 was formed first; but, as time passed, 78 epimerized in situ to product 77. After 30 min at room temperature, 78 was obtained in 35% yield along with 77 in 31% yield. There results show that the C9 setereocenter is prone to epimerization under both acidic and basic conditions. Compound 77 was also obtained almost exclusively from 75 in 63% yield when the DBU elimination was quenched after a short period of time.

H H H O O O TFA, CH2Cl2 O O + O rt, 8 min PMBO O O O HO HO HO HO HO OTBS OTBS OTBS

74 75 (8%) 76 (50%)

1) SOCl2, Et3N, o CH2Cl2, 0 C 1) SOCl2, Et3N, CH Cl , 0 oC 2) DBU, CH2Cl2, 2 2 o 0 C, 10 min 2) DBU, CH2Cl2, 0 oC, 30 min

H O H H O O O + O O HO O HO O HO O OTBS OTBS OTBS

77 (63%) 77 (35%) 78 (31%) DBU, CH Cl , 0 oC 2 2

Scheme 4.6 First Dehydration 42 Alcohols 77 and 78 could also be produced from lactone 62 (Scheme 4.7). The same reaction sequence as its diastereomer 61 was utilized, albeit in lower yields. Interestingly, the SmI2-mediated reductive dehydroxylation of 82 gave one major diastereomer.

OH OH HO O OsO , THF/Pyr.; O 4 O (COCl)2, DMSO O

H2S; 60% Et3N, CH2Cl2 PMBO O PMBO O PMBO O HO HO 65% HO OTBS OTBS OTBS

62 79 80

H H O O SmI , THF/t-BuOH TFA, CH Cl 2 O 2 2 O 41% 54% O O PMBO HO HO HO OTBS OTBS 81 82

H H O 1) SOCl2, Et3N, O o CH2Cl2, 0 C O + O 2) DBU, CH Cl , 2 2 O O 0 oC HO HO OTBS OTBS 77 (32%) 78 (25%)

Scheme 4.7 Preparation of 77 and 78 from 62

43 4.4 Second Dehydration and the End Game

The dehydration of cyclobutanol 77 was further investigated. Both Martin surfurane

and Burgess reagent68 proved to have no effect. Recourse was then made to form the triflate of 77 first and then subject it to the elimination conditions (Scheme 4.8). The triflate 83 was successfully prepared when an excess amount of freshly distilled triflic anhydride was used69 and the reaction mixture was quenched with isopropyl alcohol.

Triflate 83 was relatively stable and could be purified by flash silica gel column chromatography. Nevertheless, triflate 83 was subjected to elimination immediately after the column chromatographic purification. The elimination was carried out with DBU at room temperature and monitored by NMR in C6D6. As it turned out, the elimination required 3 eq. of DBU. Clearly compound 84 was formed first. As time passed by, more and more of the less polar epimerization product 85 was formed. At longer reaction time, starting material 83 had been completely consumed and products 84 and 85 were formed in a ratio of approximately 2:3. Compounds 84 and 85 could be easily separated by flash column chromatography and were safe for storage for a few days when frozen in benzene without detectable decomposition.

44 H H O O Tf2O, Pyr., CH2Cl2; O O i-PrOH O HO O TfO OTBS OTBS 77 83

DBU, Benzene, rt

H H O O

O + O

O O

OTBS OTBS 84 (21%) 85 (35%)

Et3N•(HF)3, CH3CN, Et3N, rt; 57%

H O

OH (+)-1

Scheme 4.8 Total Synthesis of Fomannosin (1)

45 With the penultimate compound in hand, the time had come for the final

deprotection of the TBS ether. The reaction of compound 84 with TBAF at 0 oC resulted

70 in decomposition. A much milder desilylation reagent, Et3N(HF)3, was called upon for the final deprotection. To our pleasure, the reaction of 85 with an excess amount of

Et3N(HF)3 in actonitrile in the presence of 30% (v/v) triethylamine delivered (+)-1 in

57% yield.

Fomannosin demonstrated far greater stability in deuterated dichloromethane than deuterated chloroform. Hence, deuterated dichloromethane was used as solvent for NMR studies. The spectroscopic properties of the synthetic fomannosin closely resembled those of the natural product (see Table 1, Table 2, and the experimental section). Due to the inherent instability of fomannosin, the synthetic fomannosin was always contaminated with impurities. The purification of fomannosin proved not to be trivial. After the final product was purified by flash column chromatography, the initial 1H NMR spectrum (see appendix) showed that besides the H2O peak (singlet at 1.52 ppm) and Me4Si peak

(singlet at 0.08 ppm) from the deuterated solvent, the final product was accompanied with small amounts of the desilylation reagent Et3N(HF)3 (quartet at 3.44 ppm, J = 7.0

Hz, triplet at 1.15 ppm, J = 7.0 Hz which overlaps with one of methyl groups of fomannosin) and solvent impurities (grease, multiplet at 0.93-0.85 ppm). When the synthetic fomannosin was further purified by preparative thin-layer chromatography,

Et3N(HF)3 was successfully removed (see appendix). However, this extra operation also led to substantial loss of material and incorporation of new impurity/impurities (possibly the dimerization of fomannosin) as some peaks from different impurities still persisted

(see appendix). Due to the limited amount of sample, no further purification was possible.

5a Natural (CDCl3, 270 MHz) Synthetic (CD2Cl2, 500 MHz)* 1H NMR, (mult, J) 1H NMR, (mult, J) H-6 6.90 (d, J = 2.4 Hz) 6.89 (d, J = 2.4 Hz) H-5 6.70 (d, J = 2.4 Hz) 6.68 (d, J = 2.4 Hz) H-8a 4.91 (d, J = 10.1 Hz) 4.86 (d, J = 10.3 Hz) H-1a 4.43 (d, J = 13.7 Hz) 4.37 (d, J = 13.4 Hz) H-1b 4.35 (d, J = 13.7 Hz) 4.30 (d, J = 13.4 Hz) H-8b 4.29 (d, J = 10.1 Hz) 4.25 (d, J = 10.1 Hz) H-9 3.18 (dd, J = 9.0, 12.1 Hz) 3.15 (dd, J = 8.2, 10.2 Hz) 3.07-3.05 (m) OH 2.64 (s) H-12a 2.23 (d, J = 18.3 Hz) 2.19 (d, J = 16.3 Hz) 2.06 (s) H-12b 1.95 (d, J = 18.3 Hz) 1.95 (d, J = 19.1 Hz) H-10a 1.74 (ddd, J = 2.4, 9.0, 12.8 Hz) 1.74-1.72 (m) 1.67 (m) 1.60 (m) H-10b 1.57 (dd, J = 12.1, 12.8 Hz) Overlap with H2O peak 1.36 (t, J = 7.3 Hz) 1.27 (s) CH3 1.16 (s) 1.15 (s) CH3 1.10 (s) 1.08 (s)

Table 1. Comparison of 1H NMR Data for Synthetic and Natural Fomannosin

______* The 1H NMR spectrum of fomannosin after first purification was used for comparison.

7b Natural (CDCl3, ) Synthetic (CD2Cl2, )** C-13 219.10 218.37 C-3 166.15 165.72 C-4 155.05 154.85 C-5 146.76 147.96 C-6 139.93 139.53 C-2 114.09 - C-8 73.95 73.50 C-1 58.56 58.52 C-12 53.58 53.61 C-7 52.77 52.79 C-9 46.70 46.60 C-10 38.41 38.39 C-11 33.86 32.94 CH3 29.90 29.65 CH3 28.34 27.89

Table 2. Comparison of 13C NMR Data for Synthetic and Natural Fomannosin

______** Due to limited sample, the 13C data were obtained through HSQC and HMBC experiments.

CHAPTER 5

EXPERIMENTAL SECTION

(-)-(3aR,5R,6aS)-Methyl Dihydro-2,2-dimethyl-5H-furo[2,3-d][1,3]dioxole-5-

carboxylate (15).14 A solution of 1316 (67.0 g, 162 mmol) in methanol (1650 mL) was treated with 2.5M sulfuric acid (84 mL), stirred at rt for 16 h, neutralized with concentrated sodium hydroxide solution, and freed of solvent. The residue was taken up into dichloromethane (1000 mL) and the solution was dried and evaporated to provide the diol which was used without further purification.

The above material was dissolved in THF (875 mL) and cooled to 0 °C before a solution of NaIO4 (52 g, 243 mmol) in H2O (700 mL) was introduced. The reaction mixture was stirred at rt overnight, the solvent was evaporated, and the residue was triturated with ethyl acetate (500 mL). The organic layer was washed with water (2300 mL) and brine (200 mL). The aqueous layers were further extracted with ethyl acetate (3 x 200 mL), and the combined organic layers were dried and evaporated to give the aldehyde which was used directly.

The crude aldehyde was dissolved in CH3CN (440 mL), treated with aqueous

NaH2PO4 solution (33.7 g, 244 mmol, in 120 mL of H2O), followed by hydrogen

49 peroxide (25 mL of 30%), and cooled to 0 °C. Following the addition of sodium chlorite

(22.1 g, 244 mmol, in 120 mL of H2O), the reaction mixture was warmed to rt and stirred overnight. The CH3CN was evaporated and the mixture was extracted with ethyl acetate

(2 x 300 mL). The aqueous layer was acidified with citric acid to pH 1-2 and extracted with ethyl acetate (2 x 200 mL). The combined organic layers were washed with brine

(300 mL), dried, concentrated to approximately 300 mL, and treated with diazomethane until N2 effervescence stopped. The solvent was evaporated, and the methyl ester was dissolved in dichloromethane (300 mL) and treated sequentially with DMAP (2.0 g, 16 mmol), triethylamine (3.5 mL, 25 mmol), and tosyl chloride (5.0 g, 26 mmol). The resulting solution was stirred at rt overnight, diluted with ether (500 mL), and filtered.

The filtrate was washed with CuSO4 (300 mL) and NaHCO3 solutions (200 mL), and brine (200 mL). The organic layer was dried and evaporated to leave the crude methyl ester.

The above material was dissolved in dichloromethane (400 mL), treated with

DBU (25.2 g, 166 mmol), and stirred at rt for 5 h. The reaction mixture was concentrated to 100 mL, diluted with ethyl acetate (200 mL), and filtered through a silica gel pad.

Solvent evaporation furnished the α,β-unsaturated ester which was taken up into EtOH

(100 mL) and hydrogenated over 5% Pd/C (1.3 g) under H2 (40 psi) for 1 h. The mixture was filtered through Celite and concentrated. The residue was subjected to chromatography on silica gel (elution with hexanes/ethyl acetate 3:2) to give 15 (29.4 g,

90% for 5 steps) as a colorless oil; IR (film, cm-1) 1757, 1734, 1438; 1H NMR (300 MHz,

CDCl3) δ 5.78 (d, J = 3.4 Hz, 1 H), 4.63 (t, J = 4.2 Hz, 1H), 4.55 (dd, J = 9.2, 0.9 Hz, 1

H), 3.69 (s, 3H), 2.59 (dd, J = 14.1, 0.5 Hz, 1 H), 2.23 (ddd, J = 14.1, 9.2, 4.8 Hz, 1 H), 50 13 1.38 (s, 3 H), 1.21 (s, 3 H); C NMR (75 MHz, CDCl3) δ 172.0, 112.4, 106.8, 79.3, 76.9,

+ 24 51.8, 34.8, 25.2 (2 C); HRMS (ES) m/z (M+Na) calcd 225.0733, obsd 225.0740; [α]D -

63.3 (c 1.03, CHCl3).

(-)-(2R,4S,5R)-Methyl 4-(4-Methoxybenzyloxy)tetrahydro-5-methoxyfuran-2-

carboxylate (16).14 A solution of 15 (5.00 g, 24.7 mmol) in methanol (100 mL) was treated with 37% HCl (1.3 mL) and refluxed for 1 h before being neutralized with solid

NaHCO3 (5 g). The solvent was evaporated and the residue was dissolved in dichloromethane (300 mL), dried, and evaporated to give a mixture of acetals. This material was taken up directly into dichloromethane (100 mL), treated with p- methoxbenzyl trichloroacetimidate (9.21 g, 32.6 mmol) and CSA (380 mg, 1.63 mmol) at

0 °C. The reaction mixture was stirred at 0 °C for 1 day and at rt for 2 days, diluted with saturated NaHCO3 solution, and extracted with dichloromethane. The combined organic layers were washed with brine and dried prior to solvent evaporation. The residue was purified by MPLC (elution with hexanes/ethyl acetate 7:3) to afford 16 (3.88 g) and 17

(1.1 g) in 88% combined yield over 2 steps.

For 16: colorless oil; IR (film, cm-1) 1759, 1731, 1613; 1H NMR (300 MHz,

CDCl3) δ 7.21 (m, 2 H), 6.86 (m, 2 H), 5.10 (s, 1 H), 4.63 (dd, J = 9.0, 4.5 Hz, 1 H), 4.43 s, 2 H), 3.93 (dd, J = 5.5, 2.1 Hz, 1 H), 3.79 (s, 3 H) (s, 3H), 3.37 (s, 3 H), 2.46 (ddd, J =

13.5, 9.0, 5.5 Hz, 1 H), 2.27 (ddd, J = 13.5, 4.5, 2.1 Hz, 1 H); 13C NMR (75 MHz,

CDCl3) δ 172.4, 159.3, 129.7, 129.2 (2C), 108.0, 81.1, 75.8, 55.2, 55.0, 52.2, 34.0;

+ 24 HRMS (ES) m/z (N+Na) calcd 319.1152, obsd 319.1161; [α]D -27.4 (c 1.96, CHCl3).

The C4-epimer 17 was contaminated with inseparable impurities and was not fully characterized. 51 (2S,4S,5R)-Methyl 4-(4-Methoxybenzyloxy)tetrahydro-2-(tert-butyldiphenyl

silyloxymethyl)-5-methoxyfuran-2-carboxylate (18) and its C4-epimer 19.14 A solution of diisopropylamine (10.2 mL, 72.8 mmol) in THF (80 mL) was treated with n- butyllithium (1.5 M in hexane, 36 mL, 54 mmol) at -30 °C and stirred for 20 min before being cooled to -78 °C. A solution of 16 (10.8 g, 36.4 mmol) in THF (30 mL) was added dropwise. The reaction mixture was stirred for 1 h, at which point a solution of monomeric formaldehyde in THF was added until a light brown color developed. The resulting mixture was warmed to -10 °C, quenched with saturated NH4Cl solution (50 mL), and diluted with ethyl acetate (500 mL) and H2O (200 mL). The separated aqueous layer was extracted with ethyl acetate. The combined organic layers were dried and evaporated to leave a residue that was purified by chromatography on silica gel (elution with hexanes/ethyl acetate 2:3) to give the 4β-hydroxymethyl furanoside (7.03 g, 59%) and its C4-epimer (4.08 g, 34%).

For the 4β-hydroxymethyl furanoside: colorless oil: IR (film, cm-1) 1733, 1613,

1 1586; H NMR (300 MHz, CDCl3) δ 7.16 (m, 2H), 6.82 (m, 2 H), 5.05 (s, 1 H), 4.38

(ABq, J = 11.4 Hz, ∆ν = 14.2 Hz, 2H), 3.91 (d, J = 4.3 Hz, 1 H), 3.80 (d, J = 11.4 Hz, 1

H), 3.74 (s, 3 H), 3.67 (s, 3 H), 3.61 (d, J = 11.4 Hz, 1 H), 3.36 (s, 3 H), 2.52 (br s, 1 H),

13 2.43 (d, J = 13.8 Hz, 1 H), 2.21 (dd, J = 13.8, 4.9 Hz, 1 H); C NMR (75 MHz, CDCl3) δ

172.9, 159.1, 129.4, 129.0 (2 C), 113.6 (2 C), 108.4, 88.3, 81.4, 70.4, 67.0, 55.2, 55.0,

+ 24 52.4, 34.8; HRMS (ES) m/z (M+Na) calcd 349.1258, obsd 349.1249; [α]D -39.1 (c

1.71, CHCl3).

52 For the 4α-hydroxymethyl furanoside: colorless oil; IR (film, cm-1) 1737, 1613,

1 1586; H NMR (300 MHz, CDCl3) δ 7.22 (m, 2H), 6.86 (m, 2 H), 5.01 (s, 1 H), 4.44

(ABq, J = 11.3 Hz, ∆ν = 15.5 Hz, 2 H), 3.96 (d, J = 5.0 Hz, 1 H), 3.80 (ABq, J = 11.3

Hz, ∆ν = 19.9 Hz, 2 H), 3.78 (s, 3 H), 3.75 (s, 3 H), 3.39 (s, 3 H), 2.63 (br s, 1 H), 2.50

13 (dd, J = 14.3, 5.6 Hz, 1 H), 2.18 (d, J = 14.3 Hz, 1 H); C NMR (75 MHz, CDCl3) δ

173.3, 159.4, 129.3 (2 C), 129.2, 113.9 (2 C), 107.9, 87.3, 81.3, 70.9, 67.0, 55.2, 54.8,

+ 24 52.3, 35.1; HRMS (ES) m/z (M+Na) calcd 349.1258, obsd 349.1235; [α]D -53.9 (c

1.33, CHCl3).

A solution of the 4β-hydroxytmethyl furanoside (41.2 g, 43.4 mmol) and imidazole (14.8 g, 217 mmol) in dichloromethane (150 mL) was treated with tert- butyldiphenylsilyl chloride (14.3 g, 52.1 mmol), stirred at rt for 3 h, and quenched with

H2O (300 mL). The mixture was extracted with ethyl acetate and the combined organic layers were dried prior to solvent evaporation. The residue was purified by column chromatography on silica gel (elution with hexanes/ethyl acetate 7:1) to give 18 (22.7 g,

-1 1 93%) as a colorless oil; IR (film, cm ) 1765, 1730, 1514; H NMR (300 MHz, CDCl3) δ

7.73-7.65 (m, 4 H), 7.41 (m, 6 H), 7.22 (m, 2 H), 6.86 (m, 2 H), 5.15 (s, 1 H), 4.43 (s, 2

H), 3.98 (d, J = 10.1 Hz, 1 H), 3.90 (d, J = 4.1 Hz, 1 H), 3.80 (s, 3 H), 3.74 (d, J = 10.1

Hz, 1 H), 3.73 (s, 3 H), 3.33 (s, 3 H), 2.55 (d, J = 13.7 Hz, 1 H), 2.06 (dd, J = 13.7, 4.7

13 Hz, 1 H), 1.05 (s, 9 H); C NMR (75 MHz, CDCl3) δ 173.3, 159.2, 135.6 (2 C), 133.1,

133.0, 129.8, 129.7 (2 C), 129.1 (2 C), 127.7 (2 C), 127.6 (2 C), 113.7 (2 C), 108.0, 88.6,

81.1, 70.3, 69.5, 55.2, 54.8, 52.3, 35.6, 26.6 (3 C), 19.2; HRMS (ES) m/z (M+Na)+ calcd

24 587.2436, obsd 587.2410; [α]D -13.8 (c 2.68, CHCl3);

53 The C4-epimer 19 was similarly prepared (92% for silylation) as a colorless oil;

-1 1 IR (film, cm ) 1738, 1614, 1586; H NMR (300 MHz, CDCl3) δ 7.65 (m, 4 H), 7.37 (m,

6 H), 7.13 (m, 2 H), 6.82 (m, 2 H), 4.96 (s, 1 H), 4.37 (s, 2 H), 4.03 (d, J = 9.5 Hz, 1 H),

3.96 (dd, J = 6.0, 1.4 Hz, 1 H), 3.88 (d, J = 9.5 Hz, 1 H), 3.80 (s, 3 H), 3.75 (s, 3 H), 3.36

(s, 3 H), 2.72 (dd, J = 14.2, 6.0 Hz, 1 H), 2.11 (dd, J = 14.2, 1.4 Hz, 1 H), 1.04 (s, 9 H);

13 C NMR (75 MHz, CDCl3) δ 173.2, 159.2, 135.7 (2 C), 135.6 (2 C), 133.4, 133.2, 129.8,

129.6 (2 C), 129.1 (2 C), 127.6 (2C), 127.6 (2 C), 113.8 (2 C), 108.0, 87.2, 82.3, 70.9,

68.9, 55.3, 54.7, 52.1, 35.4, 26.7 (3 C), 19.3; HRMS (ES) m/z (M+Na)+ calcd 587.2436,

24 obsd 587.2477; [α]D -31.7 (c 3.29, CHCl3).

(-)-((2S,3R,5R)-4-(4-Methoxybenzyloxy)tetrahydro-5-methoxy-3-vinylfuran-

2-yl)methanol tert-Butyldiphenylsilyl Ether (20).14 A solution of 18 (1.28 g, 2.91 mmol) in dichloromethane (915 mL) was treated with a solution of DIBAL-H in hexanes

(1.0 M, 8.7 mL, 8.7 mmol) at -78 °C, allowed to warm to -20 °C, and stirred for 1 h. The mixture was quenched with a 20% solution of sodium potassium tartrate (20 mL) and stirred until clear phase separation was achieved. The aqueous phase was extracted with dichloromethane. The combined organic phases were washed with brine and dried prior to evaporation to give an oily residue.

A solution of DMSO (1.2 mL, 17 mmol) in dichloromethane (20 mL) was slowly treated with oxalyl chloride (0.33 mL, 3.8 mmol) at -78 °C. The reaction mixture was stirred for 20 min before a solution of the above residue in dichloromethane (7 mL) was introduced. The reaction mixture was stirred at -78 °C for 1 h before being quenched with triethylamine (3.0 mL, 22 mmol), warmed to rt, diluted with saturated NaHCO3 54 solution (20 mL), and extracted with dichloromethane. The combined organic phases were washed with brine, dried, and filtered through a silica gel pad before evaporation.

The residue was used directly.

A suspension of methyltriphenylphosphonium bromide (1.54 g, 4.32 mmol) in

THF (20 mL) was treated with a solution of n-BuLi in hexanes (1.50 M, 2.50 mL, 3.75 mL) and stirred at -30 °C for 20 min before a solution of the above residue in THF (8 mL) was introduced. The mixture was warmed to rt and stirred for 3 h before being quenched with saturated NaHCO3 solution (5 mL). The mixture was taken into ethyl acetate (300 mL), washed with brine, dried and concentrated. The reside was purified by flash chromatography on silica gel (elusion with hexanes/ethyl acetate 15:1) to give 20

(942 mg, 79%) as a colorless oil; IR (film, cm-1) 1613, 1588, 1514, 1464; 1H NMR (300

MHz, CDCl3) δ 7.67 (m, 4 H), 7.40 (m, 6 H), 7.24 (m, 2 H), 6.87 (m, 2 H), 6.10 (dd, J =

17.4, 10.8 Hz, 1 H), 5.34 (dd, J = 17.4, 1.6 Hz, 1 H), 5.13 (dd, J = 10.8, 1.6 Hz, 1 H),

5.01 (s, 1 H), 4.44 (s, 2 H), 3.97 (ddd, J = 6.1, 2.6, 1.0 Hz, 1 H), 3.80 (s, 3 H), 3.62 (s, 2

H), 3.28 (s, 3 H), 2.35 (dd, J = 13.5, 6.1 Hz, 1 H), 2.01 (dd, J = 13.5, 2.6 Hz, 1 H), 1.07

13 (s, 9 H); C NMR (75 MHz, CDCl3) δ 159.2, 141.0, 135.7 (4 C), 133.5 (2 C), 130.1,

129.6 (2 C), 129.2 (2 C), 127.6 (4 C), 113.8 (2 C), 113.3, 108.2, 87.0, 83.2, 70.8, 69.8,

55.3, 54.7, 37.2, 26.8 (3 C), 19.3; HRMS (ES) m/z (M+Na)+ calcd 555.2537, obsd

24 555.2537; [α]D -14.8 (c 2.04, CHCl3).

(-)-((2R,3R,5R)-4-(4-Methoxybenzyloxy)tetrahydro-5-methoxy-2-vinylfuran-

3-yl)methanol tert-Butyldiphenylsilyl Ether (21).14 Vinylated furanoside 21 was similarly prepared (74% for 3 steps) and isolated as a colorless oil; IR (film, cm-1) 1613, 55 1 1586, 1514; H NMR (300 MHz, CDCl3) δ 7.67 (m, 4 H), 7.34 (m, 6 H), 7.18 (m, 2 H),

6.84 (m, 2 H), 6.12 (dd, J = 17.4, 10.8 Hz, 1 H), 5.33 (dd, J = 17.4, 1.6 Hz, 1 H), 5.11

(dd, J = 10.8, 1.6 Hz, 1 H), 4.95 (d, J = 1.1 Hz, 1 H), 4.42 (s, 2 H), 3.99 (ddd, J = 6.1, 3.3,

1.1 Hz, 1 H), 3.81 (s, 3 H), 3.77 (d, J = 9.5 Hz, 1 H), 3.64 (d, J = 9.5 Hz, 1 H), 3.38 (s, 3

H), 2.40 (dd, J = 13.5, 3.3 Hz, 1 H), 2.10 (dd, J = 13.5, 6.1 Hz, 1 H), 1.07 (s, 9 H); 13C

NMR (75 MHz, CDCl3) δ 159.2, 141.6, 135.7 (2 C), 135.7 (2 C), 133.6, 133.6, 130.1,

129.5 (2 C), 129.5 (2 C), 129.1 (2 C), 127.5 (2 C), 113.8 (2 C), 113.2, 108.4, 87.0, 83.1,

71.0, 69.3, 55.3, 55.1, 36.5, 26.9 (3 C), 19.4; HRMS (ES) m/z (M+Na)+ calcd 555.2537,

24 obsd 555.2537; [α]D -51.8 (c 1.70, CHCl3).

(-)-(3aS,5S,6R,6aS)-Methyl Dihydro-5-tert-butyldiphenylsiloxymethyl)-2,2- dimethyl-5H-furo[3,2-d][1,3]dioxole-6-carboxylate (22). To a THF solution (10 mL) of diisopropylamine (1.40 mL, 10 mmol) cooled to -30 °C was added n-butyllithium (1.5 M in hexanes, 3.33 mL, 5.0 mmol) and the resulting solution was stirred for 20 min in the cold before proceeding to -78 °C. Ester 15 (1.01 g, 5.00 mmol) in 6 mL of THF was quickly introduced and 1 h was allowed to elapse before a THF solution (15 mL) of formaldehyde was added. The resulting mixture was warmed to -10 °C, quenched with saturated NH4Cl solution (1 mL), and partitioned between ethyl acetate (300 mL) and water (50 mL). The separated aqueous phase was evaporated, the residue was dissolved in 1:1 methanol/ethyl acetate, and this solution was filtered through Celite. After drying and evaporation of the filtrate, the residue was subjected to MPLC on silica gel (elution with 2:3 hexanes/ethyl acetate) to give the alcohol (550 mg, 52% based on recovered 15) as a white solid, mp 103-104 °C; IR (film, cm-1) 3499, 1751, 1257; 1H NMR (300 MHz, 56 CDCl3) δ 5.84 (d, J = 3.4 Hz, 1 H), 4.70 (t, J = 4.0 Hz), 3.80-3.71 (m, 1 H), 3.74 (s, 3 H),

3.54 (dd, J = 7.2, 11.6 Hz, 1 H), 2.65 (d, J = 14.2 Hz, 1 H), 2.56 (t, J = 6.7 Hz, 1 H), 2.19

13 (dd, J = 4.7, 14.2 Hz, 1 H), 1.42 (s, 3 H), 1.26 (s, 3 H); C NMR (75 MHz, CDCl3) δ

178.6, 112.6, 106.5, 88.2, 80.2, 66.1, 52.4, 35.8, 25.5; HRMS (ES) m/z (M+Na)+ calcd

255.0839, obsd 255.0861.

To a DMF solution (15 mL) of the above alcohol (900 mg, 3.88 mmol) and imidazole (1.32 g, 19.4 mmol) was added tert-butyldiphenylsilyl chloride (1.28 g, 4.66 mmol), and the reaction mixture was stirred overnight at rt before being quenched with water (100 mL) and extracted with ethyl acetate (3 x 100 mL). After drying and evaporation of the combined organic layers, the product was chromatographed on silica gel (elution with 7:1 hexanes/ethyl acetate) to furnish 22 (1.64 g, 90%) as a colorless oil;

-1 1 IR (film, cm ) 1766, 1732, 1428; H NMR (300 MHz, CDCl3) δ 7.66 (m, 4 H), 7.39 (m,

6 H), 5.90 (d, J = 3.5 Hz, 1 H), 4.74 (dd, J = 3.5, 4.9 Hz, 1 H), 3.85 (d, J = 10.4 Hz, 1 H),

3.94 (s, 3 H), 3.69 (d, J = 10.4 Hz, 1 H), 2.72 (d, J = 14.2 Hz, 1 H), 2.29 (dd, J = 4.9, 14.2

13 Hz, 1 H), 1.48 (s, 3 H), 1.31 (s, 3 H), 1.03 (s, 9 H); C NMR (75 MHz, CDCl3) 172.7,

135.6 (2 C), 132.9, 132.7, 129.8, 127.8, 112.5, 106.8, 88.6, 80.3, 67.6, 52.3, 36.5, 26.6,

+ 22 26.0, 25.9, 19.2; HRMS (ES) m/z (M+Na) calcd 493.2017, obsd 493.2027; [α]D -28.2

(c 1.43, CHCl3).

(+)-((3aS,5S,6R,6aS)-Dihydro-2,2-dimethyl-6-vinyl-5H-furo[3,2-d][1,3]dioxol-

5-yl)methanol tert-Butyldiphenylsilyl Ether (23). To a dichloromethane solution of 22

(905 mg, 1.92 mmol) cooled to -78 °C was added diisobutylaluminum hydride (4.8 mL of

1.0 M in hexanes). The reaction mixture was stirred at this temperature for 2 h prior to 57 being quenched with methanol (1 mL) and 20% sodium potassium tartrate solution (20

mL). Stirring was maintained until clear phase separation was achieved. The aqueous layer was extracted with dichloromethane (3 x 100 mL) and the combined organic phases were washed with brine, dried, and evaporated to leave the aldehyde that was used directly without purification.

To a solution of methyltriphenylphosphonium bromide (2.13 g, 5.97 mmol) in

THF (15 mL) was added n-butyllithium (3.3 mL of 1.5 M in hexanes) at -30 °C and stirring was maintained for 20 min before the above aldehyde dissolved in THF (10 mL) was introduced. The reaction mixture was allowed to warm to rt, stirred for 3 h, quenched with saturated NaHCO3 solution (5 mL) and diluted with ethyl acetate (300 mL). The organic phase was washed with brine, dried and freed of solvent, and the residue was purified by chromatography on silica gel (elution with 15:1 hexanes/ethyl acetate) to provide 682 mg (81% over two steps) of 23 as a colorless oil; IR (film, cm-1)

1 1428, 1213, 1113; H NMR (300 MHz, CDCl3) δ 7.67 (m, 4 H), 7.40 (m, 6 H), 5.99 (d, J

= 3.9 Hz, 1 H), 5.95 (dd, J = 10.9, 17.4 Hz, 1 H), 5.33 (dd, J = 1.3, 17.4 Hz, 1 H), 5.10

(dd, J = 1.3, 10.9 Hz, 1 H), 4.88 (m, 1 H), 3.58 (d, J = 10.6 Hz, 1 H), 3.37 (d, J = 10.6

Hz, 1 H), 2.54 (dd, J = 6.5, 13.8 Hz, 1 H), 2.14 (dd, J = 1.4, 13.8 Hz, 1 H), 1.51 (s, 3 H),

13 1.34 (s, 3 H), 1.05 (s, 9 H); C NMR (75 MHz, CDCl3) δ 139.6, 135.6 (2 C), 133.2,

132.9, 129.7 (2 C), 127.7, 114.8, 112.5, 106.7, 88.6, 82.0, 69.4, 38.0, 26.9, 26.8, 19.2;

+ 22 HRMS (ES) m/z (M+Na) calcd 461.2199, obsd 461.2123; [α]D +0.40 (c 1.97, CHCl3).

Anal. Calcd for C26H34O4Si: C, 71.19; H, 7.81. Found: C, 71.30; H, 7.82.

58 (-)-(2R,3S,5R)-5-((tert-Butyldiphenylsilyloxy)methyl)-2-methoxy-5-vinyl-

tetrahydrofuran-3-ol (24) and (+)-(2S,3S,5R)-5-((tert-Butyldiphenylsilyloxy)methyl)-

2-methoxy-5-vinyl-tetrahydrofuran-3-ol (25). To a solution of 23 (370 mg, 12.2 mmol)

in methanol (92 mL) was added a solution of concentrated HCl (2.0 mL) in methanol (8

mL) at rt. The reaction mixture was stirred for 1.5 h, quenched with solid NaHCO3, and freed of methanol. The residue was dissolved in dichloromethane, dried, and concentrated. Flash chromatography of the residue on silica gel (elution with 6:1 to 5:1 hexanes/ethyl acetate afforded 151 mg (43%) of the β-isomer 24 and 106 mg (30%) of the α-isomer 25.

-1 1 For 24: IR (film, cm ) 3438, 1472, 1428; H NMR (300 MHz, CDCl3) δ 7.68-

7.65 (m, 4 H), 7.46-7.34 (m, 6 H), 6.20 (dd, J = 17.8, 17.3 Hz, 1 H), 5.48 (dd, J = 1.6,

17.2 Hz, 1 H), 5.18 (dd, J = 1.6, 10.7 Hz, 1 H), 4.94 (s, 1 H), 4.16-4.09 (m, 1 H), 3.60 (s,

2 H), 3.28 (s, 3 H), 2.34 (dd, J = 5.2, 13.7 Hz, 1 H), 1.95 (d, J = 13.6 Hz,1 H), 1.09 (s, 9

13 H); C NMR (75 MHz, CDCl3) δ 143.0, 135.78, 135.75, 133.5, 133.4, 129.8, 127.7,

113.5, 110.1, 87.0, 76.9, 70.5, 54.6, 39.6, 26.9, 19.5; HRMS (ES) m/z (M+Na)+ calcd

22 435.1962, obsd 435.1961; [α]D -21.5 (c 1.05, CHCl3).

-1 1 For 25: IR (film, cm ) 3558, 1428; H NMR (300 MHz, CDCl3) δ 7.69-7.64 (m,

4 H), 7.46-7.35 (m, 6 H), 5.93 (dd, J = 10.8, 17.4 Hz, 1 H) 5.26 (dd, J = 1.4, 17.3 Hz, 1

H), 5.05 (dd, J = 1.4, 10.8 Hz, 1 H), 4.89 (d, J = 4.6 Hz, 1 H), 4.52-4.45 (m, 1 H), 3.50

(d, J = 10.4 Hz, 1 H), 3.49 (s, 3 H), 3.44 (d, J = 10.4 Hz, 1 H), 2.58 (dd, J = 8.1, 12.1 Hz,

13 1 H) 1.78 (dd, J = 9.4, 12.1 Hz, 1 H), 1.06 (s, 9 H); C NMR (75 MHz, CDCl3) δ 141.1,

135.8, 135.7, 133.3, 129.9, 129.8, 127.8, 113.6, 103.1, 85.6, 72.7, 69.4, 55.3, 39.4, 27.0,

59 + 22 19.4; HRMS (ES) m/z (M+Na) calcd 435.1962, obsd 435.1966; [α]D +78.4 (c 0.84,

CHCl3).

(-)-((2S,3R,5R)-4-(4-Methoxybenzyloxy)tetrahydro-5-methoxy-3-vinylfuran-

2-yl)methanol tert-Butyldiphenylsilyl Ether (20) from O-Benzylation of 24. Sodium

hydride (1.15 g of 60% mineral oil dispersion, 28.6 mmol) was added in one portion into a solution of 24 (9.85 g, 23.9 mmol) in 220 mL of DMF at 0 °C. After 2 min, a solution of p-methoxybenzyl bromide (5.28 g, 26.3 mmol) in 30 mL of DMF was introduced dropwise and stirring was maintained at rt for 4 h. After quenching with saturated

NaHCO3 solution and dilution with ethyl acetate and water, the separated aqueous phase was extracted with ethyl acetate and the combined organic layers were washed with brine, dried, and concentrated to afford 20 (10.85 g, 82%) as a colorless oil spectroscopically identical to the material described above.

(+)-(((2R,4S,5S)-4-(4-Methoxybenzyloxy)-5-methoxy-2-vinyl- tetrahydrofuran-2-yl)methoxy)(tert-butyl)diphenylsilane (26). Sodium hydride (1.08 g of 60% mineral oil dispersion, 26.9 mmol) was added in one portion into a solution of

25 (8.54 g, 20.7 mmol) in 200 mL of DMF at 0 °C. After 2 min, a solution of p- methoxybenzyl bromide (4.99 g, 24.8 mmol) in 25 mL of DMF was added dropwise and stirring was maintained at rt for 1 h. Following the introduction of 0.2 equiv each of additional sodium hydride and the bromide, agitation was prolonged for 2 h and the predescribed workup protocol was followed. There was isolated 9.06 g (82%) of 26 as a

-1 1 colorless oil; IR (film, cm ) 1613, 1512; H NMR (300 MHz, CDCl3) δ 7.65-7.61 (m, 4 60 H), 7.45-7.34 (m, 6 H), 7.27-7.25 (m, 2 H), 6.87-6.82 (m, 2 H), 5.91 (dd, J = 10.9, 17.4

Hz, 1 H), 5.21 (dd, J = 1.3, 17.4 Hz, 1 H), 5.03 (dd, J = 1.3, 10.9 Hz, 1 H), 4.80 (d, J =

4.3 Hz, 1 H), 4.52 (m, 2 H), 4.26-4.18 (m, 1 H), 3.79 (s, 3 H), 3.50-3.41 (m, 5 H), 2.43

(dd, J = 8.1, 12.7 Hz, 1 H), 2.01 (dd, J = 10.5, 11.7 Hz, 1 H), 1.01 (s, 9 H); 13C NMR (75

MHz, CDCl3) δ 159.4, 141.1, 135.8, 135.7, 133.4, 133.2, 130.2, 129.84, 129.77, 129.75,

127.8, 113.9, 113.7, 102.3, 84.6, 78.5, 72.2, 69.4, 55.4, 35.9, 26.9, 19.4; HRMS (ES) m/z

+ 22 (M+Na) calcd 555.2537, obsd 555.2516; [α]D +59.5 (c 0.80, CHCl3).

(-)-(1S,2R,4R)-4-(4-Methoxybenzyloxy)-2-tert-butyldiphenylsiloxymethyl)-2-

vinylcyclobutanol (27) and (+)-[1R,2R,4R)-4-(4-Methoxybenzyloxy)-2-tert-

butyldiphenylsiloxymethyl)-2-vinylcyclobutanol (28).14 A solution of zirconocene dichloride (2.68 g, 9.17 mmol) in THF (150 mL) was treated with a solution of n- butyllithium in hexanes (1.45 M, 11.0 mL, 15.9 mmol) at -78 °C. Stirring was maintained at this temperature for 1 h before a solution of 20 (3.25 g, 6.11 mmol) in THF

(25 mL) was introduced. The resulting solution was allowed to warm up slowly, stirred overnight at rt, and passed through a short silica gel column with ether. The filtrate was concentrated and purified by flash chromatography on silica gel (elution with hexanes/ethyl acetate 5:1) to give 27 (1.85 g, 60%) and 28 (0.75 g, 25%) as colorless oils.

-1 1 For 27: IR (film, cm ) 1612, 1514, 1428; H NMR (300 MHz, CDCl3) δ 7.65 (m,

4 H), 7.41 (m, 6 H), 7.27 (m, 2 H), 6.89 (m, 2 H), 5.95 (dd, J = 17.6, 10.9 Hz, 1 H), 5.26

(dd, J = 10.9, 1.3 Hz, 1 H), 5.09 (dd, J = 17.6, 1.3 Hz, 1 H), 4.46 (s, 2 H), 4.41 (m, 1 H),

4.17 (m, 1 H), 3.81 (s, 3 H), 3.64 (d, J = 10,1 Hz, 1 H), 3.46 (d, J = 10.1 Hz, 1 H), 2.57

(br s, 1 H), 2.27 (ddd, J = 12.7, 6.8, 2.3 Hz, 1 H), 2.10 (dd, J = 12.7, 4.9 Hz, 1 H), 1.06 (s, 61 13 9 H); C NMR (75 MHz, CDCl3) δ 159.3, 137.6, 135.6 (4 C), 133.3, 133.2, 129.9, 129.7

(2 C), 127.7 (4 C), 116.5, 113.8 (2 C), 71.6 , 71.3, 70.8, 67.9, 55.2, 49.9, 31.1, 26.8 (3 C),

+ 24 19.3; HRMS (ES) m/z (M+Na) calcd 525.2432, obsd 525.2429; [α]D -25.6 (c 1.28,

CHCl3).

-1 1 For 28: IR (film, cm ) 1613, 1587, 1513, 1428; H NMR (300 MHz, CDCl3) δ

7.66 (m, 4 H), 7.40 (m, 6 H), 7.29 (m, 2 H), 6.88 (m, 2 H), 5.89 (dd, J = 17.7, 11.0 Hz, 1

H), 5.30 (dd, J = 11.0, 1.1 Hz, 1 H), 5.19 (dd, J = 17.7, 1.1 Hz, 1 H), 4.49 (s, 2 H), 4.22

(d, J = 6.4 Hz, 1 H), 3.81 (s, 3 H), 3.77 (dt, J = 8.4, 6.4 Hz, 1 H), 3.65 (d, J = 10.2 Hz, 1

H), 3.50 (d, J = 10.2 Hz, 1 H), 2.13 (dd, J = 11.2, 8.4 Hz, 1 H), 1.79 (dd, J = 11.2, 8.4 Hz,

13 1 H), 1.72 (br s, 1 H), 1.09 (s, 9 H); C NMR (75 MHz, CDCl3) δ 159.1, 137.0, 135.6 (4

C), 133.4 (2 C), 130.4, 129.7 (2 C), 129.4 (2 C), 127.7 (4 C), 117.1, 113.7 (2 C), 78.0,

75.1, 70.5, 67.3, 55.2, 45.4, 27.7, 26.9 (3 C), 19.4; HRMS (ES) m/z (M+Na)+ calcd

24 525.2432, obsd 525.2433; [α]D +10.2 (c 0.66, CHCl3).

(-)-(1R,2S,3R)-3-(4-Methoxybenzyloxy)-2-(tert-butyldimethylsilyloxy)-1-((tert- butyldiphenylsilyloxy)methyl)cyclobutanecarbaldehyde (29).15 A solution of 27

(2.637 g, 5.245 mmol) in dichloromethane (10 ml) was treated with imidazole (1.786 g,

26.23 mmol) and TBSCl (1.187 g, 7.868 mmol) at 0 oC. The reaction mixture was stirred

o at 0 C for 15 min and then at rt for 9 h before being quenched with saturated NaHCO3 solution. The mixture was diluted with ethyl acetate, washed with water and brine, dried, and concentrated. The residue was purified by silica gel chromatography (elution with hexanes/ethyl acetate 30:1) to give the TBS ether (2.940 g, 91%) as a colorless oil; IR

-1 1 (film, cm ) 1613, 1514, 1472; H NMR (300 MHz, CDCl3) δ 7.65 (m, 4 H), 7.40 (m, 6 62 H), 7.27 (m, 2 H), 6.86 (m, 2 H), 6.17 (dd, J = 17.8, 11.0 Hz, 1 H), 5.11 (dd, J = 11.0, 1.4

Hz, 1 H), 4.94 (dd, J = 17.8, 1.4 Hz, 1 H), 4.57 (d, J = 11.6 Hz, 1 H), 4.52 (dd, J = 5.2,

1.9 Hz, 1 H), 4.37 (d, J = 11.6 Hz, 1 H), 4.06 (dt, J = 6.8, 5.2 Hz, 1 H), 3.81 (s, 3 H), 3.55

(ABq, J = 10.3 Hz, ∆ν = 34.3 Hz, 2 H), 2.21 (ddd, J = 12.1, 6.9, 2.3 Hz, 1 H), 2.02 (dd, J

= 12.1, 4.9 Hz, 1 H), 1.07 (s, 9 H), 0.91 (s, 9 H), 0.06 (s, 3 H), 0.04 (s, 3 H); 13C NMR

(75 MHz, CDCl3) δ 159.0, 139.3 (4 C), 135.7 (2 C), 133.4, 131.0, 129.7 (2 C), 129.1 (2

C), 127.7 (4 C), 114.1, 113.6 (2 C), 72.8, 72.1, 70.5, 67.1, 55.3, 49.7, 31.8, 26.9 (3 C),

25.9 (3 C), 19.4, 18.4, -4.6, -4.7; HRMS (ES) m/z (M+Na)+ calcd 639.3296, obsd

24 639.3297; [α]D +0.73 (c 1.1, CHCl3).

Five drops of a 0.1% solution of Sudan III in dichloromethane were added to a solution of the TBS ether (0.219 g, 0.355 mmol) in dichloromethane (8 ml). The resulting

o red solution was cooled to -78 C. A stream of O3 was passed through the solution at -78 oC until the color disappeared. Triphenylphospine (0.140 g, 0.532 mmol) was added. The solution was allowed to warm slowly to rt and stirred at rt for 1 h. The solution was concentrated. The residue was purified by silica gel chromatography (elution with hexanes/ethyl acetate 15:1) to give 29 (0.200 g, 91%) as a red oil; IR (film, cm-1) 1714,

1 1514, 1249; H NMR (300 MHz, CDCl3) δ 10.10 (s, 1 H), 7.65-6.85 (series of m, 14 H),

3.84 (d, J = 10.9 Hz, 1 H), 3.81 (s, 3 H), 3.73 (d, J = 10.9 Hz, 1 H), 2.22 (dd, J = 13.2, 3.6

Hz, 1 H), 2.14 (ddd, J = 12.8, 6.1, 1.3 Hz, 1 H), 1.06 (s, 9 H), 0.87 (s, 9 H), 0.07 (s, 3 H),

13 0.03 (s, 3 H); C NMR (75 MHz, CDCl3) δ 204.8, 159.1, 135.6 (4 C), 133.0, 133.0,

129.8, 129.2 (2 C), 129.2 (2 C), 127.8 (4 C), 113.7 (2 C), 74.2, 71.4, 70.8, 62.5, 59.4,

55.3, 26.9 (3 C), 26.5, 25.7 (3 C), 19.3, 18.1, -4.9, -5.0; HRMS (ES) m/z (M+Na)+ calcd

24 641.3089, obsd 641.3091; [α]D -30.4 (c 1.19, CHCl3). 63 (-)-1-((1R,2S,3R)-3-(4-Methoxybenzyloxy)-2-(tert-butyldimethylsilyloxy)-1-

((tert-butyldiphenylsilyloxy)methyl)cyclobutyl)-3,3-dimethylhex-5-en-1-one (31).15 A solution of 5-iodo-4,4-dimethylpent-1-ene (22.00 g, 98.23 mmol) in pentane (650 ml) was treated with t-BuLi (1.36 M in pentane, 144.5 ml, 196.5 mmol) at -78 °C under argon. The milky solution was stirred at -78 °C for 1 h. A solution of 29 (30.40 g, 49.12 mmol) in THF (490 ml) was added at -78 °C. The reaction mixture was stirred at -78 °C for 1 h and quenched with brine at -78 °C. The suspension was allowed to warm to rt and diluted with ether and water. The organic layer was washed with brine, dried and concentrated. The residue was purified by filtering through a short pad of silica gel, and eluting with hexanes/ethyl acetate (20:1) to give carbinol 30 (33.92 g, 96%) as a colorless

-1 1 oil; IR (film, cm ) 3532, 1614, 1514; H NMR (500 MHz, CDCl3) δ 7.68-6.89 (series of m, 14 H), 5.86-5.78 (m, 1 H), 5.01-4.94 (m, 2 H), 4.71-4.67 (m, 2 H), 4.48 (d, J = 11.3

Hz, 1 H), 4.42 (d, J = 11.3 Hz, 1 H), 4.06 (dt, J = 5.9, 2.2 Hz, 1 H), 4.00 (d, J = 10.7 Hz,

1 H), 3.84 (s, 3 H), 3.59 (d, J = 10.7 Hz, 1 H), 3.23 (s, 1 H), 2.04-1.96 (m, 3 H), 1.45 (d, J

= 12.9 Hz, 1 H), 1.17-1.06 (m, 2 H), 1.10 (s, 9 H), 0.94 (s, 9 H), 0.91 (s, 3 H), 0.89 (s, 3

13 H), 0.14 (s, 3 H), 0.12 (s, 3 H); C NMR (125 MHz, CDCl3) δ 159.0, 136.0, 135.6 (4 C),

133.5, 133.4, 130.5, 129.6 (2 C), 129.1 (2 C), 127.7 (4 C), 116.6, 113.5 (2 C), 74.5, 70.8,

70.0, 69.7, 62.1, 55.2, 53.0, 47.1, 42.5, 32.9, 27.1, 27.1, 27.0 (3 C), 26.9, 25.8 (3 C), 19.3,

+ 24 18.1, -4.6, -5.3; HRMS (ES) m/z (M+Na) calcd 739.4184, obsd 739.4185; [α]D -33.9

(c 1.07, CHCl3).

A solution of 30 (107 mg, 0.149 mmol) in dichloromethane (5 ml) was treated with 4 Å MS (430 mg) and pyridinium dichromate (196 mg, 0.522 mmol). The suspension was stirred at rt for 24 h, treated with Celite, and diluted with ether. The 64 mixture was filtered through a pad of silica gel and concentrated. The residue was purified by silica gel chromatography (elution with hexanes/ethyl acetate 20:1) to give 31

(89 mg, 83%) as a colorless oil; IR (film, cm-1) 1707, 1514, 1249; 1H NMR (300 MHz,

CDCl3) δ 7.64-6.84 (series of m, 14 H), 5.88-5.69 (m, 1 H), 5.02-4.92 (m, 2 H), 4.43 (d, J

= 5.9 Hz, 1 H), 4.37 (d, J = 5.9 Hz, 1 H), 4.32-4.29 (m, 1 H), 3.83-3.80 (m, 1 H), 3.82 (s,

3 H), 3.81 (d, J = 10.2 Hz, 1 H), 3.59 (d, J = 10.2 Hz, 1 H), 2.69-2.53 (m, 3 H), 2.12 (d, J

= 7.5 Hz, 2 H), 2.02-1.96 (m, 1 H), 1.05 (s, 9 H), 0.99 (s, 6 H), 0.88 (s, 9 H), 0.03 (s, 3

13 H), 0.03 (s, 3 H); C NMR (75 MHz, CDCl3) δ 208.9, 159.0, 135.7 (2 C), 135.7, 135.6

(2 C), 133.0, 130.6, 129.8 (2 C), 129.3 (4 C), 127.8 (2 C), 116.9, 113.5 (2 C), 73.5, 72.2,

69.8, 67.0, 59.5, 55.3, 51.4, 46.5, 45.1, 33.1, 30.0, 27.1, 26.9 (3 C), 25.9 (3 C), 19.3, 18.4,

+ 23 -4.7, -4.8; HRMS (ES) m/z (M+Na) calcd 737.4028, obsd 737.4034; [α]D -42.6 (c

1.14, CHCl3).

(-)-1-(((1R,2S,3R)-2-(tert-Butyldimethylsilyloxy)-3-((tert-butyldiphenylsilyloxy)

methyl)-3-(4,4-dimethylhepta-1,6-dien-2-yl)cyclobutoxy)methyl)-4-methoxybenzene

(32). 15 A solution of ketone 31 (89.1 mg, 0.125 mmol) in pentane-toluene (1:1, 6 ml) was treated with a solution of TMSCH2Li in pentane (0.75 M, 1.00 ml, 0.748 mmol) at -78

°C. The mixture was stirred at -78 °C for 2 h. The cooling bath was removed and the reaction mixture was immediately quenched with water. The mixture was extracted with ethyl acetate, washed with brine, dried, and concentrated. The crude product was taken into benzene (5 ml), treated with pTSA•H2O (2.4 mg, 0.0125 mmol), and stirred at rt for

5 h. Three drops of triethylamine were added to quench the reaction. The mixture was concentrated. The residue was purified by silica gel chromatography (elution with 65 hexanes/ethyl acetate 30:1) to give diene 32 (74.0 mg, 83%) as a colorless oil; IR (film,

-1 1 cm ) 1513, 1248, 1112, 1075; H NMR (300 MHz, CDCl3) δ 7.68-6.84 (series of m, 14

H), 5.87-5.76 (m, 1 H), 5.08 (br s, 1 H), 5.02-4.92 (m, 2 H), 4.89 (d, J = 1.0 Hz, 1 H),

4.39 (s, 2 H), 4.39-4.35 (m, 1 H), 3.96-3.90 (m, 1 H), 3.82 (s, 3 H), 3.56 (s, 2 H), 2.34

(dd, J = 11.4, 7.1 Hz, 1 H), 2.28-2.18 (m, 2 H), 2.05-1.96 (m, 2 H), 1.82 (d, J = 15.2 Hz,

1 H), 1.60 (s, 9 H), 0.90 (s, 9 H) 0.85 (s, 3 H), 0.84 (s, 3 H), 0.04 (s, 3 H), 0.03 (s, 3 H);

13 C NMR (75 MHz, CDCl3) δ 145.5, 135.9, 135.7 (4 C) , 133.5, 133.4, 131.1, 129.6,

129.1 (2 C) 127.8, 127.7 (2 C), 127.7 (2 C), 116.7, 115.1, 113.6 (2 C), 75.3, 70.7, 69.8,

68.9, 55.2, 51.7, 47.6, 45.1, 44.5, 33.8, 27.5, 27.1, 26.9 (3 C), 26.0 (3 C), 19.3, 1.4, -4.4, -

+ 23 4.7; HRMS (ES) m/z (M+Na) calcd 735.4235, obsd 735.4265; [α]D -47.0 (c 1.26,

CHCl3).

(-)-1-(((1R,2S,3R)-2-(tert-Butyldimethylsilyloxy)-3-((tert-butyldiphenyl silyloxy)methyl)-3-(4,4-dimethylcyclopent-1-enyl)cyclobutoxy)methyl)-4- methoxybenzene (33). 15 A solution of the second-generation Grubbs catalyst (78.6 mg,

5 mol %, 0.0925 mmol) in benzene (20 ml) was added dropwise into a refluxing solution of 32 (1.32 g, 1.85 mmol) in benzene (400 ml). The reaction mixture was refluxed for 6 h, filtered through a short pad of silica gel, washed with hexanes/ethyl acetate (10:1), and concentrated. The residue was purified by silica gel chromatography (elution with hexanes/ethyl acetate 40:1) to give cyclopentene 33 (1.152 g, 91%) as a colorless oil; IR

-1 1 (film, cm ) 1514, 1248, 1112; H NMR (500 MHz, CDCl3) δ 7.67-6.84 (series of m, 14

H), 5.32 (t, J = 1.9 Hz, 1 H), 4.49-4.47 (m, 1 H), 4.48 (d, J = 11.5 Hz, 1 H), 4.40 (d, J =

11.5 Hz, 1 H), 3.99 (dd, J = 12.0, 5.5 Hz, 1 H), 3.82 (s, 3 H), 3.62 (d, J = 10.1 Hz, 1 H), 66 3.49 (d, J = 10.1 Hz, 1 H), 2.24-2.11 (m, 6 H), 1.05 (s, 9 H), 1.04 (s, 3 H), 1.03 (s, 3 H),

13 0.89 (s, 9 H), 0.04 (s, 3 H), 0.02 (s, 3 H); C NMR (125 MHz, CDCl3) δ 158.8, 142.5,

135.7 (2 C), 135.7 (2 C), 133.6, 133.5, 131.1, 129.6 (2 C), 129.1 (2 C), 127.6 (4 C),

124.7, 113.5 (2 C), 73.3, 72.7, 70.0, 67.4, 55.2, 49.2, 48.9, 47.7, 38.1, 31.6, 30.0, 30.0,

26.9 (3 C), 26.0 (3 C), 19.3, 18.4, -4.9 (2 C); HRMS (ES) m/z (M+Na)+ calcd 707.3922,

22 obsd 707.3915; [α]D -26.7 (c 0.70, CHCl3).

(-)-((1R,2S,3R)-3-(4-Methoxybenzyloxy)-2-(tert-butyldimethylsilyloxy)-1-(4,4- dimethylcyclopent-1-enyl)cyclobutyl)methanol (40). Tetrabutylammonium fluoride

(0.226ml, 1.0 M solution in THF) and acetic acid (13.6 mg, 0.226 mmol) were mixed in a plastic tube at room temperature. A solution of 33 (0.062 mg, 0.0905 mmol) in 3 ml of dry THF was added. The reaction mixture was stirred at room temperature for 70 h before being quenched with saturated NaHCO3 aqueous solution. The mixture was diluted with

EtOAc and water. The organic layer was washed twice with brine, dried over MgSO4, filtered and concentrated. The residue was purified by flash column chromatography

(silica gel, elution with hexanes/EtOAc 10:1) to afford 40 (31.4 mg, 78%) as a colorless

-1 1 oil; IR (CHCl3, cm ) 3453, 2951, 1613, 1514, 1249; H NMR (500 MHz, CDCl3) δ 7.28-

7.27 (m, 2H), 6.88-6.87 (m, 2H), 5.49 (t, J = 1.9 Hz, 1H), 4.48 (d, J = 11.6 Hz, 1H), 4.42

(d, J = 11.6 Hz, 1H), 4.19 (dd, J = 2.6, 5.3 Hz, 1H), 4.01 (dd, J = 5.7, 12.0 Hz, 1H), 3.83

(s, 3H), 3.64 (d, J = 10.6 Hz, 1H), 3.39 (d, J = 10.6 Hz, 1H), 2.28-2.08 (m, 6H), 1.11 (s,

13 3H), 1.09 (s, 3H), 0.91 (s, 9H), 0.07 (s, 3H), 0.06 (s, 3H); C NMR (125 MHz, CDCl3) δ

159.0, 142.1, 130.9, 129.2, 126.7, 113.6, 74.7, 72.5, 70.1, 66.8, 55.3, 49.1, 48.3, 47.7,

67 38.3, 32.5, 30.0, 29.9, 25.9, 18.4, -4.6, -4.8; HRMS (ES) m/z (M + Na)+ calcd 469.2745,

22 obsd 469.2752; [α]D –55.8 (c 0.51, CHCl3).

(-)-((1R,2S,3R)-3-(4-Methoxybenzyloxy)-2-(tert-butyldimethylsilyloxy)-1-(4,4- dimethylcyclopent-1-enyl)cyclobutyl)methyl 2-(Diethoxyphosphoryl)acrylate (41).

Compound 40 (9.4 mg, 0.021 mmol), fragment 36 (10.9 mg, 0.053 mmol), and EDCI

(14.1 mg, 0.074 mmol) were dissolved in 2 ml of dichloromethane. The resulting clear solution was stirred at room temperature for 1 h. The reaction mixture was concentrated.

The residue was purified by flash column chromatography (silica gel, elution with

-1 hexanes/EtOAc 2/1) to afford 40 (10.0 mg, 75%) as a colorless oil. IR (CHCl3, cm )

1 2930, 2858, 1726, 1513, 1249, 1027; H NMR (500 MHz, CDCl3) δ 7.28-7.26 (m, 2H),

6.96 (dd, J = 1.7, 41.9 Hz, 1H), 6.89-6.86 (m, 2H), 6.79 (dd, J = 1.7, 20.4 Hz, 1H), 5.47

(t, J = 1.9 Hz, 1H), 4.52 (d, J = 11.5 Hz, 1H), 4.41 (d, J = 11.5 Hz, 1H), 4.32 (dd, J = 1.9,

5.4 Hz, 1H), 4.25 (d, J = 11.2 Hz, 1H), 4.22-4.13 (m, 5H), 4.08-4.05 (m, 1H), 3.82 (s,

3H), 2.27-2.11 (m, 6H), 1.35 (dt, J = 1.5, 7.0 Hz, 6H), 1.09 (s, 3H), 1.06 (s, 3H), 0.90 (s,

13 9H), 0.06 (s, 3H), 0.05 (s, 3H); C NMR (125 MHz, CDCl3) δ 163.90, 163.76, 159.98,

143.79, 143.65, 133.86, 132.38, 130.84, 129.11, 126.05, 113.57, 73.56, 72.97, 70.26,

69.17, 62.72, 62.67, 55.26, 48.82, 47.73, 47.38, 38.29, 31.63, 29.89, 25.91, 18.32, 16.42,

16.40, 16.37, 16.35, -4.68, -4.77; HRMS (ES) m/z (M + Na)+ calcd 659.3140, obsd

22 659.3148; [α]D –30.6 (c 0.50, CHCl3).

(-)-(1S,2R,4R)-4-(4-Methoxybenzyloxy)-2-(4,4-dimethylcyclopent-1-enyl)-2-

(hydroxymethyl)cyclobutanol (43). A solution of 33 (103 mg, 0.150 mmol) in THF (5 68 ml) was treated with TBAF (0.45 ml of 1.0 M in THF), stirred at rt overnight, and concentrated. The residue was chromatographed on silica gel (elution with hexanes/ethyl

-1 acetate 2:1) to provide 38 mg (76%) of 43 as a waxy semi-solid; IR (CHCl3, cm ) 3425,

1 1613, 1515, H NMR (500 MHz, CDCl3) δ 7.30-7.28 (m, 2 H), 6.91-6.89 (m, 2H), 5.53

(t, J = 1.9 Hz, 1 H), 4.46 (s, 2H), 4.13-4.11 (m, 2 H), 3.83 (s, 3 H), 3.64 (dd, J = 0.5, 10.7

Hz, 1 H), 3.62 (d, J = 10.7 Hz, 1 H), 2.30-2.16 (m, 6 H), 1.11 (s, 3 H), 1.10 (s, 3 H); 13C

NMR (125 MHz, CDCl3) δ 159.4, 142.0, 129.8, 129.6, 128.0, 113.9, 72.3, 71.6, 70.7,

66.3, 55.3, 48.4, 47.8, 47.5, 38.8, 32.5, 29.8, 29.7; HRMS (ES) m/z (M+Na)+ calcd

22 355.1880, obsd 355.1876; [α]D -43.7 (c 0.375, CHCl3).

(-)-((1R,2S,3R)-3-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-2-

hydroxycyclobutyl)methyl 2-(Diethoxyphosphoryl)acrylate (42). Compound 43 (10.3 mg, 0.031 mmol), fragment 36 (16.1 mg, 0.078 mmol), and EDCI (20.8 mg, 0.108 mmol) were dissolved in 2 ml of dichloromethane. The resulting clear solution was stirred at room temperature for 10 min. The reaction mixture was concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 1:1) to

-1 afford 42 (13.2 mg, 75%) as a colorless oil; IR (CHCl3, cm ) 3418, 2924, 1724, 1612,

1 1514, 1249, 1026; H NMR (300 MHz, CDCl3) δ 7.27-7.24 (m, 2H), 6.98 (dd, J = 1.6,

41.8 Hz, 1H), 6.89-6.86 (m, 2H), 6.77 (dd, J = 1.6, 20.3 Hz, 1H), 5.50 (s, 1H), 4.44 (s,

2H), 4.26-4.08 (m, 8H), 3.80 (s, 3H), 2.65 (d, J = 9.2 Hz, 1H), 2.23-2.10 (m, 5H), 1.31

13 (dt, J = 1.4, 7.0 Hz, 6H), 1.05 (s, 3H), 0.94 (s, 3H); C NMR (75 MHz, CDCl3) δ 159.48,

144.24, 144.17, 141.10, 134.19, 131.74, 129.65, 127.66, 113.96, 101.57, 71.75, 71.33,

71.05, 69.20, 62.85, 62.80, 62.77, 55.41, 48.40, 47.64, 46.95, 38.85, 31.89, 29.91, 29.79, 69 + 22 16.54, 16.45 ; HRMS (ES) m/z (M + Na) calcd 545.2275, obsd 545.2299; [α]D –24.8

(c 0.66, CHCl3).

((1R,3R)-3-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-2- oxocyclobutyl)methyl 2-(Diethoxyphosphoryl)acrylate (35). IBX (46.6 mg, 0.166 mmol) was added in one portion into a solution of 42 (29.0 mg, 0.056 mmol) in 3 ml

DMSO at rt. The resulting clear solution was stirred at rt for 8 h. The reaction mixture was diluted with EtOAc, washed with brine three times, dried over MgSO4, filtered, and concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 1:1 to 2:3)) to afford 35 (16.1 mg, 55%) as a colorless oil;

1 H NMR (500 MHz, CDCl3) δ 7.28 (d, J = 8.6 Hz, 2H), 6.97 (dd, J = 1.4, 41.4 Hz, 1H),

6.88 (d, J = 8.6 Hz, 2H), 6.77 (dd, J = 1.4, 20.1 Hz, 1H), 5.58 (s, 1H), 4.97 (dd, J = 7.3,

9.8 Hz, 1H), 4.69 (d, J = 11.3 Hz, 1H), 4.54 (d, J = 11.3 Hz, 1H), 4.33 (d, J = 11.2 Hz,

1H), 4.28 (d, J = 11.2 Hz, 1H), 4.24-4.08 (m, 4H), 3.80 (s, 3H), 2.52 (dd, J = 10.0, 11.9

Hz, 1H), 2.22-2.04 (m, 5H), 1.34-1.31 (m, 6H), 1.06 (s, 6H); 13C NMR (125 MHz,

CDCl3) δ 207.8, 163.5, 163.4, 159.5, 144.8, 137.2, 133.2, 131.7, 129.8, 129.4, 126.5,

113.9, 84.9, 72.1, 66.4, 63.2, 62.9, 62.81, 62.77, 62.72, 47.5, 47.4, 38.4, 30.2, 29.5, 16.35,

16.28.

(-)-(2R,3aR,4aR,8S,8aS)-Allyl 4a-(4,4-Dimethylcyclopent-1-enyl)-2-(4-methoxy phenyl)-7-oxohexahydro-2,4-dioxabicyclo[3.2.0]hept-5-eno[7,1-c]pyran-8- carboxylate (50). A solution of monoallyl malonic acid 44 (17.3 mg, 0.120 mmol) in 2 ml of dry dichloromethane was added dropwise into a stirring solution of 43 (42.0 mg, 70 0.126 mmol) and EDCI (24.2 mg, 0.126 mmol) in 8 ml of dry dichloromethane at 0 oC.

The reaction mixture was stirred at 0 oC for 20 min, then at rt for 40 min before being concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 6:1) to afford a sticky oil (41.0 mg), which was shown by

NMR to be a mixture of 47 and 48 (~ 10%).

A mixture of 47 and 48 (46.0 mg) was dissolved in 5 ml of distilled DMSO at rt.

IBX (140.4 mg, 0.500 mmol) was added in one portion. The reaction mixture was stirred at rt for 8 h before being diluted with EtOAc and H2O. The organic phase was washed with brine twice, dried over MgSO4 and concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 8:1) to afford a yellowish oil (34.2 mg), which was shown by NMR to be a mixture of 45 and 49 (~ 1:1).

A suspension of a mixture of 45 and 49 (0.109 g, 0.239 mmol) and 4 Å molecular sieves (0.300 g) in 20 ml of dry dichloromethane was stirred at rt for 20 min before DDQ

(0.081 g, 0.357 mmol) was added. The reaction mixture was stirred at rt under argon for

24 hours before being quenched with saturated NaHCO3 solution and diluted with

EtOAc. The organic phase was washed with brine, dried over MgSO4 and concentrated.

The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 8:1) to afford 50 (56.8 mg, 28% over 3 steps) as a colorless oil; IR (neat,

-1 1 cm ) 2952, 1756, 1742, 1614, 1246; H NMR (500 MHz, CDCl3) δ 7.40 (d, J = 8.6 Hz,

2H), 6.88 (d, J = 8.6 Hz, 2H), 6.03-5.95 (m, 1H), 5.92 (s, 1H), 5.67 (s, 1H), 5.43 (d, J =

17.1 Hz, 1H), 5.32 (d, J = 10.5 Hz, 1H), 5.02 (dd, J = 5.5, 1.9 Hz, 1H), 4.82-4.75(m,

2H), 4.37 (d, J = 12.1 Hz, 1H), 4.08 (s, 1H), 4.03 (d, J = 12.1 Hz, 1H), 3.83 (s, 3H), 2.48

(dd, J = 14.0, 2.0 Hz, 1H), 2.42 (dd, J = 14.0, 5.7 Hz, 1H), 2.30-2.04 (m, 4H), 1.04 (s,

71 13 3H), 0.94 (s, 3H); C NMR (125 MHz, CDCl3) δ 167.5, 166.2, 160.7, 138.4, 131.3,

129.6, 128.7 (2C), 128.4, 119.2, 113.6 (2C), 108.2, 84.0, 75.8, 70.9, 66.4, 55.3, 52.5,

47.9, 47.4, 46.0, 38.8, 31.0, 30.0, 29.5; HRMS (ES) m/z (M + Na)+ calcd 477.1884, obsd

22 477.1902; [α]D –35.3 (c 0.58, CHCl3).

(-)-(2R,3aR,4aR,8aS)-4a-(4,4-Dimethylcyclopent-1-enyl)-2-(4-methoxyphenyl)- tetrahydro-2,4-dioxabicyclo[3.2.0]hept-5-eno[7,1-c]pyran-7(8H)-one (51).

Morpholine (0.025 ml in 0.1 ml of THF, 0.290 mmol) was added to a solution of 50 (13.2 mg, 0.029 mmol) and Pd(PPh3)4 (3.4 mg, 0.0029 mmol) in 2 ml of dry THF under argon.

The reaction mixture was stirred at rt for 10 min before being concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc

5:1) to afford 51 (7.0 mg, 65%) as a colorless oil. IR (neat, cm-1) 2950, 1757, 1615, 1518,

1 1249; H NMR (500 MHz, CDCl3) δ 7.43 (d, J = 8.7 Hz, 2H), 6.90 (d, J = 8.7 Hz, 2H),

5.76 (s, 1H), 5.65 (s, 1H), 4.42 (dd, J = 5.9, 2.4 Hz, 1H), 4.37 (d, J = 11.9 Hz, 1H), 4.03

(d, J = 11.9 Hz, 1H), 3.84 (s, 3H), 3.04 (d, J = 15.4 Hz, 1H), 2.87 (d, J = 15.4 Hz, 1H),

2.47 (dd, J = 14.0, 2.3 Hz, 1H), 2.40 (dd, J = 14.0, 5.9 Hz, 1H), 2.37-2.08 (m, 4H), 1.06

13 (s, 3H), 0.98(s, 3H); C NMR (125 MHz, CDCl3) δ 170.5, 160.8, 139.1, 128.7 (3C),

127.8, 113.7 (2C), 106.3, 82.5, 76.3, 71.3, 55.3, 47.9, 47.4, 44.3, 38.8, 37.5, 31.1, 30.0,

+ 22 29.6; HRMS (ES) m/z (M + Na) calcd 393.1672, obsd 393.1659; [α]D –10.7 (c 0.61,

CHCl3).

(1S,7R)-Allyl 7-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-4-oxo-

3-oxabicyclo[4.2.0]oct-5-ene-5-carboxylate (46). A solution of a mixture of 45 and 49 72 (7.7 mg, 0.017 mmol) in 2 ml of dichloromethane was treated with 2 drops of

triethylamine at 0 oC, followed by the addition of MsCl (3.9 µl, 0.0506 mmol) and a catalytic amount of DMAP. The mixture was stirred at rt for 1 h before 8 drops of triethylamine and 2 drops of MsCl were added. The mixture was stirred at rt overnight before being diluted with ether. The resulting suspension was filtered through a short pad of silica gel, washing with ether. The combined filtrate was concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc

3:1) to afford 46 (1.8 mg, 23%, 58% based on recovered sarting material) as a colorless

1 oil; H NMR (500 MHz, CDCl3) δ 7.23 (d, J = 8.6 Hz, 2H), 6.88 (d, J = 8.6 Hz, 2H),

6.04-5.96 (m, 1H), 5.53 (s, 1H), 5.45 (dd, J = 1.4, 17.2 Hz, 1H), 5.32 (dd, J = 1.1, 10.4

Hz, 1H), 5.08 (dd, J = 1.6, 5.6 Hz, 1H), 4.84-4.74 (m, 2H), 4.62 (d, J = 11.1 Hz, 1H),

4.58 (d, J = 11.1 Hz, 1H), 4.36 (d, J = 10.3 Hz, 1H), 4.16 (d, J = 10.3 Hz, 1H), 3.82 (s,

3H), 2.39 (dd, J = 1.7, 9.4 Hz, 1H), 2.28-2.07 (m, 5H), 1.12 (s, 6H); HRMS (ES) m/z (M

+ Na)+ calcd 461.1935, obsd 461.1935;

(+)-(1R,6R,7R,Z)-7-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-

6-hydroxy-5-(hydroxymethylene)-3-oxabicyclo[4.2.0]octan-4-one (58). A solution of

EDCI (46.1 mg, 0.240 mmol) in dry dichloromethane (2 ml) was added dropwise to a solution of 43 (72.6 mg, 0.218 mmol) and ethylsulfanylcarbonyl acetic acid (35.6 mg,

0.240 mmol) in 8 ml of the same solvent at -40 °C. The reaction mixture was stirred in the cold for 2 h, allowed to warm to rt, diluted with hexanes/ethyl acetate (2:1), filtered through a short pad of silica gel, and concentrated. Chromatography of the residue on silica gel (elution with hexanes/ethyl acetate 6:1) gave 70.4 mg of colorless oil. 73 The above material was dissolved in distilled DMSO, treated with IBX (213 mg,

0.761 mmol) in one portion, and stirred at rt for 3 h before being diluted with ether and water. The separated organic phase was washed with brine (2x), dried, and concentrated.

The residue was purified by flash chromatography on silica gel (elution with hexanes/ethyl acetate 7:1) to afford a colorless oil (44 mg) shown by NMR to be a mixture of 54 and 55 (ca 5:4, 44% over 2 steps).

Triethylsilane (25.5 µL, 0.160 mmol) was added dropwise to a suspension of the above mixture (24.5 mg, 53.2 mmol) and 10% palladium on carbon (17 mg, 0.016 mmol) in 2 ml of dichloromethane at rt under argon. After being stirred for 1 h, the mixture was diluted with hexanes/ethyl acetate (2/1), filtered through a short pad of silica gel, and concentrated. The residue was purified by flash column chromatography (silica gel, hexanes/ethyl acetate 1:1) afforded 58 (15.8 mg, 74%) as a colorless oil; IR (film, cm-1)

1 3492, 1661, 1612; H NMR (500 MHz, CDCl3) δ 12.27 (d, J = 13.0 Hz, 1 H), 7.54 (d, J =

12.9 Hz, 1 H), 7.24 (d, J = 8.6 Hz, 2 H), 6.91 (d, J = 8.6 H, 2 H), 5.54 (t, J = 1.8 Hz, 1 H),

4.53 (d, J = 11.3 Hz, 1 H), 4.46 (d, J = 11.3 Hz, 1 H), 4.18 (d, J = 11.8 Hz, 1 H), 4.01 (d,

J = 11.8 Hz), 3.91 (t, J = 5.8 Hz, 1 H), 3.84 (s, 3 H), 3.42 (s, 1 H), 2.24-2.14 (m, 6 H),

13 1.09 (s, 3 H), 1.08 (s, 3 H); C NMR (125 MHz, CDCl3) δ 172.6, 166.7, 159.7, 139.8,

129.7, 129.6, 129.2, 127.8, 114.2, 114.1, 104.5, 78.8, 74.3, 72.5, 71.8, 55.3, 48.5, 47.3,

45.4, 38.8, 30.6, 24.7, 29.6; HRMS (ES) m/z (M+Na)+ calcd 423.1778, obsd 423.1779;

22 [α]D +13.4 (c 0.79, CHCl3).

74 (+)-(1R,5S,6S,7R)-7-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-

6-hydroxy-5-(hydroxymethyl)-3-oxabicyclo[4.2.0]octan-4-one (59) and (-)-

(1R,5R,6S,7R)-7-(4-Methoxybenzyloxy)-1-(4,4-dimethylcyclopent-1-enyl)-6-hydroxy-

5-(hydroxymethyl)-3-oxabicyclo[4.2.0]octan-4-one (60). Sodium borohydride (45.3

mg, 1.187 mmol) and potassium dihydrogen phosphate (815 mg, 5.99 mmol) were added simultaneously to a solution of 58 (479 mg, 1.20 mmol) in methanol (60 ml) cooled to 0

°C. After 1 h of stirring in the cold, more NaBH4 (45.3 mg, 1.30 mmol) and KH2PO4

(815 mg, 5.99 mmol) were added at 0 °C. Glacial acetic acid was then introduced through a pipet to bring the pH of the solution to 7. Small portions of NaBH4 were added at 0 °C, followed by the addition of glacial acetic acid to keep the pH neutral. This process was repeated every 5 min until the starting material disappeared almost completely. The reaction mixture was quenched with saturated NH4Cl solution, the methanol was evaporated, and the mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried, and concentrated. The residue was purified by flash chromatography (silica gel, elution with hexane/ethyl acetate 4:1 to 3:2) to afford 59 (less polar) as a colorless oil (18.5 mg. 37%) and 60 (more polar) as a sticky oil (12.9 mg,

27%).

-1 1 For 59: IR (film, cm ) 3472, 1737, 1414; H NMR (500 MHZ, CDC13) δ 7.25 (d,

J = 8.6 HZ, 2 H), 6.91, (d, J = 8.6 Hz, 2 H), 5.59 (t, J = 1.8 Hz, 1 H) 4.50 (d, J = 11.3 HZ

1 H), 4.44 (d, J = 11.3 HZ, 1 H), 4.38 (d, J = 11.9 Hz, 1 H). 4.07 (dd, J = 5.6, 11.8 HZ,1

H), 4.00 (dd, J = 4.9, 11.8 Hz, 1 H), 3.97 (d, J = 11.9 HZ,1 H), 3.92 (dd, J = 4.6, 7.5 Hz,

1 H), 3.83 (s, 3H), 3.52 (s, 1 H), 2.97 (t, J = 5.3 Hz, 1 H), 2.35-2.13 (m, 6 H), 1.114 (s, 3

13 H), 1.107 (s, 3H); C NMR (125 MHZ, CDC13) δ 173.7, 159.7, 139.1, 129.6 (2 C), 129.2, 75 128.7, 114.1 (2 C), 73.3, 71.8, 70.4, 58.3, 55.4, 49.0, 48.7, 47.5, 47.3, 39.1, 32.1, 29.81,

+ 22 29.78, 29.73; HRMS (ES) m/z (M+Na) calcd 425.1940, obsd 425.1937; [α]D + 2.51 (c

0.66, CHC13).

-1 1 For 60: IR (film, cm ) 3496, 1742, 1611; H NMR (500 MHz, CDC13) δ 7.25 (d,

J = 8.5 Hz, 2 H), 6.91 (d, J = 8.5 Hz, 2 H), 5.64 (s, 1 H), 4.54 (d, J = 11.4 Hz, 1 H), 4.47

(d, J = 11.4 Hz, 1 H), 4.39 (d, J = 11.8 Hz, 1 H), 4.20-4.15 (m, 1 H), 4.13 (d, J = 11.8 Hz,

1 H), 4.02 (dd, J = 3.6, 7.2 Hz, 1 H), 3.88-3.82 (m, 1 H), 3.84 (s, 3 H), 3.20 (s, 1 H), 2.88

(dd, J = 5.2, 7.5 Hz, 1 H), 2.54 (dd, J = 5.0, 8.6 Hz, 1 H), 2.31-2.12 (m, 6 H), 1.10 (s, 3

13 H), 1.09 (s, 3 H); C NMR (125 MHz, CDC13) δ 172.8, 159.6, 140.6, 129.4, 129.1,

128.1, 114.0, 76.2, 74.2, 71.7, 58.5, 55.3, 50.0, 48.9, 47.3, 46.7, 38.8, 32.2, 29.8, 29.7;

+ 22 HRMS (ES) m/z (M +Na) calcd 425.1935, obsd 425.1929; [α]D -2.1 (c 0.19, CHC13).

(+)-(1R,5S,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy) methyl)-1-(4,4-dimethylcyclopent-1-enyl)-6-hydroxy-3-oxabicyclo[4.2.0]octan-4-one

(61). tert-Butydimethylsilyl triflate (0.583 ml. 2.53 mmol) was added dropwise in a solution of 59 (0.204 g. 0.507 mmol) and 2,6-lutidine (1.77 ml, 15.21 mmol) in 17 ml of dry dichloromethane at -78 oC under argon. The mixture was stirred at -78 o C for 5

o min, saturated NaHCO3 solution (10 ml) was added at -78 C to quench the reaction, and the mixture was diluted with ether and allowed to warm to rt. The organic layer was washed with brine, dried, and concentrated. The residue was dried under vacuum to remove most of the 2,6-lutidine before being purified by flash chromatography (silica gel, elution with hexanes/ethyl acetate 9:1) to afford 61 (0.233 g. 89%) as a sticky oil that solidified in the refrigerator; IR (film, cm -1) 1757, 1514, 1250; 1H NMR (500 MHz, 76 CDC13) δ 7.23 (d. J = 8.5 Hz, 2 H), 6.87 (d. J = 8.5 Hz, 2 H), 5.53 (s, 1 H), 4.47 (d, J =

11.3 Hz, 1 H), 4.39 (d, J = 11.3 Hz, 1 H), 4.35 (d,. J = 11.9 Hz, 1 H), 4.15 (dd, J = 5.3,

10.3 Hz 1 H), 4.01 (dd, J = 5.3, 10.3 Hz, 1 H), 3.914 (s, 1 H), 3.912 (d, J = 11.8 Hz, 1 H),

3.85 (dd, J = 5.2, 7.0 Hz, 1 H), 3.81 (s, 3 H), 2.84 (t, J = 5.3 Hz, 1 H), 2.29-2.16 (m, 6 H),

1.09 (s, 3 H), 1.07 (s, 3 H), 0.90 (s, 9 H), 0.12 (s, 3 H), 0.10 (s, 3 H); 13C NMR (125

MHz, CDC13) δ 171.8, 159.5, 139.8, 129.8, 129.5 (2 C), 127.8, 114.0 (2 C), 77.6, 73.6,

71.2, 70.0, 59.2, 55.4, 49.3, 48.9, 47.3, 47.1, 39.0, 32.1, 29.8, 29.7, 26.0 (3 C), 18.4, -5.3,

+ 22 -5.4; HRMS (ES) m/z (M+Na) calcd 539.2805, obsd 539.2820; [α]D + 15.8 (c 0.76,

CHC13).

(-)-(1R,5R,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy)

methyl)-1-(4,4-dimethylcyclopent-1-enyl)-6-hydroxy-3-oxabicyclo[4.2.0]octan-4-one

(62). TBSOTf (0.044 ml, 0.193 mmol) was added dropwise into a solution of 60 (15.5 mg, 0.0385 mmol) and 2,6-lutidine (0.135 ml) in 5 ml of dry dichloromethane at -78 oC

o under argon. After 5 min, 4 ml of saturated NaHCO3 solution was added at -78 C to quench the reaction. The mixture was diluted with EtOAc and dichloromethane and allowed to warm to rt. The organic layer was washed with brine, dried over MgSO4, and concentrated. The residue was dried with vacuum pump to remove most of 2,6-lutidine before being purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 8:1) to afford 62 (14.7 mg, 74%)as a slightly yellow sticky oil; IR (neat,

-1 1 cm ) 2951, 2928, 2856, 1748, 1514, 1250; H NMR (500 MHz, CDCl3) δ 7.26 (d, J = 8.5

Hz, 2H), 6.90 (d, J = 8.5 Hz, 2H), 5.60 (s, 1H), 4.52 (d, J = 11.2 Hz, 1H), 4.46 (d, J =

11.2 Hz, 1H), 4.45 (d, J = 11.6 Hz, 1H), 4.18 (dd, J = 5.0, 10.5 Hz, 1H), 4.10-4.06 (m, 77 3H), 3.83 (s, 3H), 3.29 (s, 1H), 2.90 (dd, J = 5.1, 6.8 Hz, 1H), 2.30-2.14 (m, 6H), 1.09 (s,

13 6H), 0.92 (s, 9H), 0.11 (s, 6H); C NMR (125 MHz, CDCl3) δ 171.8, 159.6, 141.1,

129.7, 129.5, 127.7, 114.1, 76.7, 76.6, 73.9, 71.6, 59.1, 55.4, 50.9, 49.0, 47.4, 46.9, 38.9,

32.3, 29.9, 29.8, 26.1, 18.5, -5.3; HRMS (ES) m/z (M + Na)+ calcd 539.2799, obsd

22 539.2808; [α]D -38.4 (c 0.32, CHCl3).

(-)-(1R,5R,6S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-(4,4-dimethyl cyclopent-1-enyl)-6,7-dihydroxy-3-oxabicyclo[4.2.0]octan-4-one (64). Trifluoroacetic acid (0.05 ml) was added dropwise into a solution of 62 (7.4 mg, 0.0143 mmo) in 0.50 ml of dry dichloromethane at rt under argon. After 20 min, the reaction mixture was quenched by fast addition of saturated NaHCO3 solution. The mixture was extracted with dichloromethane twice. The combined organic layers were washed with brine, dried over

MgSO4 and concentrated. The residue was purified by flash column chromatography

(silica gel, elution with hexanes/EtOAc 7/1 with 0.5% ethanol) to afford 64 (4.1 mg,

72%) as a colorless flaky solid; IR (neat, cm-1) 3442, 2951, 1736, 1729, 1362; 1H NMR

(500 MHz, CDCl3) δ 5.61 (s, 1H), 4.37 (d, J = 11.7 Hz, 1H), 4.24 (dd, J = 5.1, 6.7 Hz,

1H), 4.16-4.12 (m, 2H), 4.08 (dd, J = 4.6, 10.3 Hz, 1H), 3.65 (s, 1H), 2.91 (dd, J = 4.7,

7.7 Hz, 1H), 2.48 (d, J = 4.7 Hz, 1H), 2.27-2.15 (m, 6H), 1.083 (s, 3H), 1.075 (s, 3H),

13 0.89 (s, 9H), 0.10 (s, 6H); C NMR (125 MHz, CDCl3) δ 171.2, 141.3, 127.9, 76.4, 73.9,

70.9, 59.5, 49.5, 49.1, 47.4, 45.9, 38.9, 35.0, 29.8, 29.7, 25.9 (3C), 18.3, -5.4, -5.5;

+ 22 HRMS (ES) m/z (M + Na) calcd 419.2231, obsd 419.2231; [α]D -51.0 (c 0.92, CHCl3).

78 (+)-(1S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-(4,4-dimethylcyclopent-1-

enyl)-7-hydroxy-3-oxabicyclo[4.2.0]oct-5-en-4-one (67). Thionyl chloride (2.87 µl,

0.0393 mmol) was added one drop a minute into a solution of 64 (13.0 mg, 0.0328 mmol) and triethylamine (13.7 µl, 0.0983 mmol) in 1.5 ml of dry dichloromethane at 0 oC under argon. After 15 min at 0 oC, the solution was poured into a mixture of EtOAc, water and a small amount of triethylamine. The organic layer was washed with brine, dried over

MgSO4, and concentrated. The solid residue was used directly for the next step without further purification.

Half of the above solid residue was taken up in 1 ml of dry dichloromethane and cooled to 0 oC. DBU (2.4 µl, 0.0196 mmol) was added at 0 oC. After 20 min at 0 oC, more DBU (4.6 µl, 0.0393 mmol) was introduced. The mixture was stirred at 0 oC for 15 more minutes. The mixture was loaded directly onto a silica gel column, eluted with hexanes/EtOAc (3:1, with 1% ethanol) to afford 67 (3.7 mg, 52% over 2 steps) as a colorless solid; IR (neat, cm-1) 3497, 2950, 1712, 1703, 1462, 1115; 1H NMR (500 MHz,

CDCl3) δ 5.57 (s, 1H), 5.12 (t, J = 5.8 Hz, 1H), 4.65 (d, J = 15.3 Hz, 1H), 4.40 (d, J =

15.3 Hz, 1H), 4.32 (d, J = 10.2 Hz, 1H), 4.17 (d, J = 10.2 Hz, 1H), 2.34 (dd, J = 6.2, 12.6

Hz, 1H), 2.22-2.16 (m, 4H), 2.09 (d, J = 6.4 Hz, 1H), 1.12 (s, 3H), 1.11 (s, 3H), 0.93 (s,

13 9H), 0.13 (s, 3H), 0.12 (s, 3H); C NMR (125 MHz, CDCl3) δ 164.0, 156.0, 141.9,

127.5, 124.3, 75.1, 71.5, 60.6, 47.4, 46.4, 39.3, 38.8, 29.6, 26.1 (3C), 18.5, -5.3, -5.4;

+ 22 HRMS (ES) m/z (M + Na) calcd 401.2124, obsd 401.2136; [α]D + 139.5 (c 0.22,

CHCl3).

79 (+)-(1S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-(4,4-dimethylcyclopent-1-

enyl)-4-oxo-3-oxabicyclo[4.2.0]oct-5-en-7-yl Methanesulfonate (68). MsCl (1.8 µl,

0.0238 mmol) was added into a solution of 67 (3.0 mg, 0.0079 mmol) and triethylamine

(5.5 µl, 0.0396 mmol) in 0.4 ml of dry dichloromethane at -30 oC under argon. After 20 min at -30 oC, the reaction mixture was diluted with EtOAc and poured into saturated

NaHCO3 solution. The organic layer was washed with brine, dried over MgSO4 and concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 3:1) to afford 68 (3.0 mg, 83%) as a colorless oil; IR (neat,

-1 1 cm ) 2950, 2924, 1728, 1509, 1464, 1363, 1180; H NMR (500 MHz, CDCl3) δ 5.81 (d,

J = 5.5 Hz, 1H), 5.57 (s, 1H), 4.62 (d, J = 14.1 Hz, 1H), 4.48 (d, J = 14.1 Hz, 1H), 4.35

(d, J = 10.2 Hz, 1H), 4.22 (d, J = 10.2 Hz, 1H), 3.04 (s, 3H), 2.62 (d, J = 13.3 Hz, 1H),

2.50 (dd, J = 5.7, 13.3 Hz, 1H), 2.25-2.19 (m, 4H), 1.15 (s, 3H), 1.14 (s, 3H), 0.94 (s,

13 9H), 0.16 (s, 3H), 0.15 (s, 3H),; C NMR (125 MHz, CDCl3) δ 163.5, 149.7, 139.0,

128.4, 127.4, 76.5, 75.4, 59.1, 48.0, 47.6, 46.3, 39.4, 37.0, 29.6, 29.5, 26.1(3C), 18.7, -

+ 22 5.23, -5.25; HRMS (ES) m/z (M + Na) calcd 479.1900, obsd 479.1915; [α]D + 120.3

(c 0.15, CHCl3).

(+)-(1S,5S,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy)

methyl)-1-((1R,2R)-1,2-dihydroxy-4,4-dimethylcyclopentyl)-6-hydroxy-3-oxa-

bicyclo[4.2.0]octan-4-one (72). Osmium tetraoxide (13.1 mg, 0.0516 mmol) was added

in one portion to a solution of 61 (25.4 mg, 0.0492 mmol) in a mixture of THF and pyridine (4:1, 1.5 ml) at 0 oC. The reaction mixture was stirred at rt for 35 min before a

o large excess of H2S gas was introduced at 0 C. After further admixture with ethyl 80 acetate, saturated NaHSO3 solution, and a small amount of water, the organic layer was washed with brine, dried, and filtered through a short pad of Celite. The filtrate was concentrated. The residue was purified by flash chromatography (silica gel, elution with hexanes/EtOAc 4:1 with 1% ethanol) to afford 72 (20.6 mg. 76%) as a colorless sticky

-1 1 oil; IR (film, cm ) 3431, 1743, 1514, 1250; H NMR (500 MHz, CDC13) δ 7.24 (d, J =

8.5 Hz, 2 H), 6.87 (d, J = 8.5 Hz, 2 H), 5.18 (s, 1 H), 4.58 (d, J = 11.3 Hz, 1 H), 4.54 (d, J

= 12.2 Hz, 1 H), 4.44 (d, J = 11.3 Hz, 1 H), 4.36 (d, J = 12.2 Hz, 1 H), 4.25-4.22 (m, 2

H), 4.07 (dd, J = 9.3, 10.9 Hz, 1 H), 3.81-3.78 (m, 4 H), 3.23 (s, 1 H), 2.95 (dd, J = 4.3,

9.2 Hz, 1 H), 2.81 (d, J = 8.4 Hz, 1 H), 2.25 (d, J = 15.0 Hz, 1 H), 2.07-2.06 (m, 2 H),

1.82 (d, J = 15.0 Hz, 1 H), 1.78 (dd, J = 7.0, 12.1 Hz, 1 H), 1.70 (d, J = 10.9 Hz, 1 H),

1.13 (s, 3 H), 1.00 (s, 3 H), 0.90 (s, 9 H), 0.14 (s, 3 H), 0.13 (s, 3 H); 13C NMR (125

MHz, CDC13) δ 170.9, 159.6, 129.6, 129.4 (2 C), 114.0 (2 C), 82.0, 78.8, 75.1, 73.3,

71.3, 69.4, 60.4, 55.4, 51.5, 50.7, 48.3, 46.9, 33.1, 32.1, 31.0, 28.9, 25.9 (3 C), 18.2, -5.4,

+ 22 -5.6; HRMS (ES) m/z (M+Na) calcd 573.2860, obsd 573.2879; [α]D +56.0 (c 1.02,

CHC13).

(+)-(1R,5S,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy)

methyl)-6-hydroxy-1-((R)-1-hydroxy-4,4-dimethyl-2-oxocyclopentyl)-3-oxabicyclo[4.2.0]octan-4-one (73). Dimethyl sulfoxide (65.4 µl, 0.921 mmol) was added dropwise to a solution of oxalyl chloride (31.6 µl, 0.368 mmol) in 2 ml of dry dichloromethane at -78 oC under argon. After 30 min at -78 oC, a solution of 72 (50.7 mg, 0.0921 mmol) in 1.3 ml of dichloromethane was added dropwise at -78 oC. After 1 h in the cold, triethylamine (0.129 ml, 0.921 mmol) was introduced dropwise at -78o C. 81 After 10 min, the reaction mixture was allowed to warm to rt and diluted with ethyl acetate and a small amount of water. The mixture was washed with brine (2x), dried, and concentrated. The residue was purified by flash chromatography (silica gel, elution with hexane/ethyl acetate 4:1 containing 1% ethanol) to afford 73 (39.6 mg, 79%) as a white

-1 1 foam; IR (film, cm ) 3299, 1753, 1515, 1464; H NMR (500 MHz, CDC13) δ 7.25 (d, J =

8.4 Hz, 2 H) 6.88 (d, J = 8.4 Hz, 2 H), 5.78 (s, 1 H), 4.63 (d, J = 10.5 Hz, 1 H), 4.39 (d, J

= 11.8 Hz, 1 H), 4.27 (d, J = 10.5 Hz, 1H) 4.22 (d, J = 11.8 Hz, 1 H), 4.15 (dd, J = 5.5,

10.6 Hz, 1 H), 4.01 (dd, J = 4.7, 10.7 Hz, 1 H), 3.92 (dd, J = 5.3, 8.9 Hz, 1 H), 3.81 (s, 3

H), 3.22 (s, 1 H), 2.76 (t, J = 5.0 Hz, 1 H), 2.39 (dd, J = 5.3, 14.8 Hz, 1 H), 2.25 (dd, J =

9.0, 14.8 Hz, 1 H), 1.93 (d, J = 14.7 Hz 1 H), 1.85 (d, J = 13.8 Hz, 1 H), 1.77 (d, J = 13.8

Hz, 1 H), 1.20 (s, 3 H), 1.11 (s, 3 H), 0.91 (s, 9 H), 0.12 (s, 3 H), 0.10 (s, 3 H); 13C NMR

(125 MHz, CDC3) δ 170.5, 159.9, 130.0 (2 C), 128.2, 119.1, 114.2 (2 C), 86.8, 86.3,

71.8, 71.7, 68.9, 58.4, 55.4, 50.5, 49.6, 48.7, 36.8, 32.6, 31.8, 29.3, 26.0 (3C) 18.5, -5.2, -

+ 22 5.3; HRMS (ES) m/z (M + Na) calcd 571.2703, obsd 571.2697; [α]D + 72.7 (c 0.88,

CHCl3).

(1R,5S,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy)

methyl)-1-(4,4-dimethyl-2-oxocyclopentyl)-6-hydroxy-3-oxabicyclo[4.2.0]octan-4-

one (74). Samarium diiodide (0.1 M in THF, 0.766 ml, 0.0766 mmol) was rapidly added

dropwise to a solution of 73 (13.6 mg, 0.0255 mmol) in a mixture of THF and tert-

butanol (4:1, 0.5 ml) at rt under argon. The solution was stirred for 15 min before being exposed to air to quench the reaction. The mixture was diluted with ethyl acetate and poured into saturated NaHCO3 solution. The separated organic layer was washed with 82 brine, dried, and concentrated. The residue was purified by flash chromatography (silica

gel, elution with hexane/ethyl acetate 6:1) to deliver 74 as a colorless viscous oil (8.4 mg,

64%) constituted of a pair of diastereomers; IR (film, cm-1) 3438, 1754, 1514; 1H NMR

(500 MHz, CDC13) δ 7.25 (d, J = 8.3 Hz, 4 H), 6.86 (d, J = 8.3 Hz, 4 H), 5.68 (s, 1 H),

5.03 (d, J = 11.4 Hz, 1 H), 4.85 (s, 1 H), 4.64 (d, J = 10.7 Hz, 1 H), 4.52 (d, J = 11.0 Hz,

1 H), 4.50 (d, J = 10.6 Hz, 1H), 4.37-4.32 (m, 4 H), 4.26 (dd, J = 11.2, 19.4 Hz, 1 H),

4.21-4.11 (m, 6 H), 4.11-3.99 (m, 5 H), 3.89-3.86 (m, 2 H), 3.81 (s, 3 H), 3.80 (s, 3 H),

3.75 (d, J = 5.7 Hz, 1 H), 3.74 (d, J = 5.8 Hz, 1 H), 3.12 (dd, J = 8.7, 12.8 Hz, 1 H), 3.07

(t, J = 5.5 Hz, 1 H), 2.99 (dd, J = 4.5, 8.1 Hz, 1 H), 2.75 (dd, J = 4.1, 6.2 Hz, 1 H), 2.66

(dd, J = 7.1, 12.5 Hz, 1 H), 2.54 (dd, J = 8.9, 14.2 Hz, 1 H), 2.39-2.33 (m, 3 H), 2.25-2.15

(m, 6 H), 2,15-2.02 (m, 6 H), 1.97-1.91 (m, 4 H), 1.19 (s, 3 H), 1.09 (s, 3 H), 1.08 (s, 3

H), 1.03 (s, 3 H), 0.91 (s, 9 H), 0.87 (s, 9 H), 0.13 (s, 3 H), 0.11 (s, 3 H), 1.10 (s, 3 H),

13 0.08 (s, 3 H); C NMR (125 MHz, CDC13) δ 171.9, 171.6, 170.9, 159.5, 130.0, 129.8,

129.7, 129.5, 124.5, 114.2, 114.0, 113.9, 78.7, 73.4, 72.6, 71.2, 71.0, 70.2, 68.4, 60.1,

59.5, 55.4, 54.2, 49.9, 49.7, 49.3, 45.7, 44.2, 39.1, 34.1, 34.0, 33.2, 30.1, 29.9, 27.7, 27.6,

26.1, 26.0, 25.9, 18.6, 18.4, 18.2, -5.2, -5.3, -5.4, -5.5; HRMS (ES) m/z (M+Na)+ calcd

555.2754, obsd 555.2767.

(+)-(1R,5S,6S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((S)-4,4-dimethyl-

2-oxocyclopentyl)-6,7-dihydroxy-3-oxabicyclo[4.2.0]octan-4-one (75) and (+)-

(1R,5S,6S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((R)-4,4-dimethyl-2-

oxocyclopentyl)-6,7-dihydroxy-3-oxabicyclo[4.2.0]octan-4-one (76). Trifluoroacetic

acid (0.5 ml) was added rapidly dropwise to a solution of 74 (53.0 mg, 0.100 mmol) in 5 83 ml of dry dichloromethane at rt under argon. After 8 min, saturated NaHCO3 solution was quickly introduced to quench the reaction. The mixture was diluted with dichloromethane, the aqueous layer was back-extracted with ethyl acetate, and the combined organic phases were washed with brine, dried, and concentrated. The residue was purified by flash chromatography (silica gel, elution with hexanes/ethyl acetate 6:1 with 0.5% ethanol) to afford 75 (3.4 mg, 8%) as a thick oil and 76 (20.7 mg, 50%) as a white solid.

-1 1 For 75: IR (film, cm ) 3415, 1736, 1463; H NMR (500 MHz, CDCl3) δ 5.29 (s, 1

H), 5.02 (d, J = 11.5 Hz, 1 H), 4.18 (dd, J = 3.9, 10.8 Hz, 1 H), 4.04 (dd, J = 8.7, 10.8 Hz,

1 H), 3.92-3.88 (m, 2 H), 3.13 (dd, J = 3.9, 8.7 Hz, 1 H), 2.91 (d, J = 7.6 Hz, 1 H), 2.35-

2.30 (m, 3 H), 2.13-2.05 (m, 2 H), 1.99 (dd, J = 5.5, 13.8 Hz, 1 H), 1.94-1.90 (m, 1 H),

1.24 (s, 3 H), 1.04 (s, 3 H), 0.88 (s, 9 H), 0.12 (s, 3 H), 0.20 (s, 3 H); 13C NMR (125

MHz, CDCl3) δ 220.1, 171.2, 78.5, 70.7, 66.6, 60.5, 53.4, 49.0, 47.2, 44.4, 42.3, 36.9,

34.1, 30.0, 27.6, 25.8 (3 C), 18.1, -5.58, -5.63; HRMS (ES) m/z (M+Na)+ calcd 435.2179,

22 obsd 435.2175; [α]D +6.1 (c 0.37, CHCl3).

-1 1 For 76: IR (film, cm ) 3415, 1753, 1463; H NMR (500 MHz, CDCl3) δ 4.72 (s, 1

H), 4.22-4.17 (m, 2 H), 4.09 (dd, J = 7.6, 10.7 Hz, 1 H), 4.00 (d, J = 11.6 Hz, 1 H), 3.91-

3.86 (m, 1 H), 3.05 (dd, J = 4.1, 7.4 Hz, 1 H), 3.00 (d, J = 9.0 Hz, 1 H), 2.73 (dd, J = 8.3,

12.6 Hz, 1 H), 2.40 (dd, J = 5.5, 13.6 Hz, 1 H), 2.33 (dd, J = 8.1, 13.6 Hz, 1 H), 2.21 (s, 2

H), 1.87 (dd, J = 8.3, 12.0 Hz, 1 H), 1.65 (t, J = 12.5 Hz, 1 H), 1.20 (s, 3 H), 1.07 (s, 3

13 H), 0.89 (s, 9 H), 0.13 (s, 3 H), 0.11 (s, 3 H); C NMR (125 MHz, CDCl3) δ 220.8,

171.2, 76.7, 69.4, 66.6, 60.0, 53.9, 49.3, 48.2, 44.4, 40.1, 35.6, 33.9, 30.0, 27.9, 25.9 (3

84 + 22 C), 18.2, -5.5, -5.6; HRMS (ES) m/z (M+Na) calcd 435.2179, obsd 435.2177; [α]D

+120.9 (c 0.34, CHCl3).

(+)-(1S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((S)-4,4-dimethyl-2- oxocyclopentyl)-7-hydroxy-3-oxabicyclo[4.2.0]oct-5-en-4-one (77) and (+)-(1S,7R)-5-

((tert-Butyldimethylsilyloxy)methyl)-1-((R)-4,4-dimethyl-2-oxocyclopentyl)-7-

hydroxy-3-oxabicyclo[4.2.0]oct-5-en-4-one (78). Thionyl chloride (1.08 µl, 0.015 mmol) was added slowly to a solution of 76 (5.1 mg, 0.012 mmol) and triethylamine

(5.17 µl, 0.037 mmol) in 0.6 ml of dry dichloromethane at 0 °C under argon. After 20 min at this temperature, the solution was poured into a mixture of ethyl acetate, water and a small amount of triethylamine. The organic layer was washed with brine, dried, and concentrated. The solid residue was immediately taken up in 1.0 ml of dry dichloromethane and cooled to 0 °C. DBU (5.6 µl, 0.037 mmol) was added at 0 °C under argon. After 30 min at 0 °C, the mixture was loaded directly onto a silica gel column, eluted with hexanes/ethyl acetate (3:1, with 1% ethanol) to afford 77 (1.7 mg, 35%) and

78 (1.5 mg, 31%), both as white solids.

-1 1 For 77: IR (film, cm ) 3456, 1725, 1463; H NMR (500 MHz, CDCl3) δ 5.09 (dt,

J = 2.4, 6.7 Hz, 1 H), 4.57 (d, J = 14.6 Hz, 1 H), 4.39 (d, J = 14.6 MHz, 1 H), 4.24 (d, J =

10.8 Hz, 1 H), 4.25 (d, J = 10.8 Hz, 1 H), 3.38 (d, J = 7.3 Hz, 1 H), 3.33 (dd, J = 8.3, 13.1

Hz, 1 H), 2.35 (dd, J = 6.6, 13.4 Hz, 1 H), 2.31 (d, J = 20.1 Hz, 1 H), 2.15 (dd, J = 2.7,

13.4 Hz, 1 H), 2.08 (d, J = 19.0 Hz, 1 H), 2.06-2.02 (m, 1 H), 1.71 (t, J = 12.8 Hz, 1 H),

1.22 (s, 3 H), 1.12 (s, 3 H), 0.92 (s, 9 H), 0.13 (s, 3 H), 0.12 (s, 3 H); 13C NMR (125

MHz, CDCl3) δ 221.1, 163.5, 125.2, 76.0, 70.6, 59.8, 54.4, 53.3, 44.8, 40.1, 38.5, 33.4, 85 30.1, 27.9, 26.1 (3 C), 18.5, -5.3, -5.4; HRMS (ES) m/z (M+Na)+ calcd 417.2073, obsd

22 417.2089; [α]D +22.4 (c 0.36, CHCl3).

-1 For 78: IR (film, cm ) 3410, 1728, 1694; 1H NMR (500 MHz, CDCl3) δ 5.13 (d,

J = 6.3 Hz, 1 H), 4.83 (d, J = 10.5 Hz, 1 H), 4.65 (dd, J = 1.0, 15.8 Hz, 1 H), 4.37 (d, J =

15.8 Hz, 1 H), 4.17 (d, J = 10.5 Hz, 1 H), 3.12 (dd, J = 8.5, 12.6 Hz, 1 H), 2.34 (dd, J =

6.7, 13.5 Hz, 1 H), 2.29 (d, J = 2.2 Hz, 1 H), 2.22-2.15 (m, 2 H), 2.07 (d, J = 18.3 Hz, 1

H), 2.02 (dd, J = 2.6, 13.4 Hz, 1 H), 1.92 (ddd, J = 2.4, 8.4, 12.8 Hz, 1 H), 1.25 (s, 3 H),

13 1.08 (s, 3 H), 0.93 (s, 9 H), 0.13 (s, 6 H); C NMR (125 MHz, CDCl3) δ 218.6, 163.7,

156.9, 125.7, 76.3, 69.9, 61.1, 54.2, 49.1, 44.3, 40.1, 35.8, 33.7, 30.0, 27.8, 26.1 (3 C),

+ 22 18.5, -5.3, -5.4; HRMS (ES) m/z (M+Na) calcd 417.2073, obsd 417.2087; [α]D +100.8

(c 0.19, CHCl3).

Equilibration of 77 and 78. A solution of 78 (2.6 mg, 6.6 µmol) in dichloromethane (0.6 ml) was treated with DBU (3.0 µl, 19.8 µmol) at rt. After 45 min at rt, the mixture was loaded directly onto a silica gel column and eluted with hexanes/ethyl acetate (3.5:1, with 1% ethanol) to afford 77 (1.4 mg, 54%) and 78 (1.2 mg, 46%).

(-)-(1S,5R,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy) methyl)-1-((1R,2R)-1,2-dihydroxy-4,4-dimethylcyclopentyl)-6-hydroxy-3-oxabicyclo[4.2.0]octan-4-one (79). Osmium tetroxide (47.9 mg, 0.189 mmol) was added in one portion into a solution of 62 (92.8 mg, 0.180 mmol) in a mixture of THF and pyridine

o (4:1, 6 ml) at 0 C. The solution was stirred at rt for 20 min before a large excess of H2S gas was passed through the solution at 0 oC. The mixture was diluted with ethyl acetate, 86 saturated NaHSO3 solution, and a small amount of water. The organic layer was washed with brine, dried over MgSO4, and filtered through a short pad of Celite. The filtrate was concentrated. The residue was purified by flash column chromatography (silica gel,

Hexane/EtOAc 4:1 with 1% ethanol) to afford 79 as a white solid (59.0 mg, 60%); IR

-1 1 (neat, cm ) 3502, 2951, 1749, 1514, 1250, 1000; H NMR (500 MHz, CDCl3) δ 7.26 (d,

J = 8.5 Hz, 2H), 6.88 (d, J = 8.5 Hz, 2H), 4.81 (s, 1H), 4.66 (d, J = 11.1 Hz, 1H), 4.53 (d,

J = 12.4 Hz, 1H), 4.45 (d, J = 11.1 Hz, 1H), 4.32 (dd, J = 8.8, 14.2 Hz, 1H), 4.19 (dd, J =

4.7, 10.7 Hz, 1H), 4.13 (dd, J = 5.5, 10.7 Hz, 1H), 4.09-4.05 (m, 2H), 3.81 (s, 3H), 3.67

(s, 1H), 2.83 (d, J = 6.0 Hz, 1H), 2.74 (t, J = 5.1 Hz, 1H), 2.26 (dd, J = 3.0, 14.2 Hz, 1H),

1.97 (dd, J = 7.3, 14.2 Hz, 1H), 1.79-1.77 (m, 2H), 1.74 (d, J = 14.6 Hz, 1H), 1.67 (d, J =

14.6 Hz, 1H), 1.13 (s, 3H), 1.01 (s, 3H), 0.91 (s, 9H), 0.12 (s, 6H); 13C NMR (125 MHz,

CDCl3) δ 171.6, 159.7, 129.7 (2C), 129.4, 114.1 (2C), 83.4, 77.7, 76.0, 74.3, 72.9, 72.1,

59.2, 55.4, 50.5, 50.2, 50.1, 46.6, 33.1, 32.2, 31.5, 30.8, 26.1 (3C), 18.5, -5.4 (2C);

+ 22 HRMS (ES) m/z (M + Na) calcd 573.2860, obsd 573.2860; [α]D - 13.6 (c 0.12,

CHCl3).

(-)-(1R,5R,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy)

methyl)-6-hydroxy-1-((R)-1-hydroxy-4,4-dimethyl-2-oxocyclopentyl)-3-oxa-

bicyclo[4.2.0]octan-4-one (80). DMSO (49.1 µl, 0.692 mmol) was added dropwise into a

o solution of (COCl)2 (23.8 µl, 0.277 mmol) in 2 ml of dry dichloromethane at -78 C under argon. After 30 min at -78 oC, a solution of 79 (38.1 mg, 0.0692 mmol) in 1.4 ml of dry dichloromethane was added dropwise at -78 oC. After 70 min at -78 oC, triethylamine

(97.2 µl, 0.692 mmol) was added dropwise at -78 oC. After 15 min, the reaction mixture 87 was allowed to warm to rt, then diluted with EtOAc and a small amount of water. The

mixture was washed with brine twice, dried over MgSO4 and concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc

3.5:1, with 1% ethanol) to afford 80 (24.9 mg, 65%) as a colorless oil; IR (neat, cm-1)

1 3483, 3298, 2953, 1746, 1515, 1252; H NMR (500 MHz, CDCl3) δ 7.27 (d, J = 8.3 Hz,

2H), 6.89 (d, J = 8.6 Hz, 2H), 5.72 (s, 1H), 4.65 (d, J = 10.6 Hz, 1H), 4.56 (d, J = 12.0

Hz, 1H), 4.34 (d, J = 10.6 Hz, 1H), 4.23 (dd, J = 4.1, 10.7 Hz, 1H), 4.18 (d, J = 12.0 Hz,

1H), 4.10-4.04 (m, 2H), 3.80 (s, 3H), 3.34 (s, 1H), 2.88 (dd, J = 4.1, 7.2 Hz, 1H), 2.45

(dd, J = 4.4, 14.9 Hz, 1H), 2.16 (d, J = 14.0 Hz, 1H), 2.07 (dd, J = 8.5, 14.9 Hz, 1H), 2.03

(d, J = 14.2 Hz, 1H), 1.93 (d, J = 15.5 Hz, 1H), 1.76 (dd, J = 1.7, 14.0 Hz, 1H), 1.16 (s,

13 3H), 1.03 (s, 3H), 0.91 (s, 9H), 0.10 (s, 3H), 0.09 (s, 3H); C NMR (125 MHz, CDCl3) δ

170.0, 159.9, 130.2 (2C), 128.1, 119.1, 114.2 (2C), 87.5, 87.3, 75.9, 72.5, 71.7, 58.8,

55.4, 52.0, 49.9, 49.0, 48.2, 38.5, 31.9, 30.7, 29.3, 26.1 (3C), 18.6, -5.2, -5.3; HRMS (ES)

+ 22 m/z (M + Na) calcd 571.2703, obsd 571.2697; [α]D – 1.6 (c 1.24, CHCl3).

(-)-(1R,5R,6S,7R)-7-(4-Methoxybenzyloxy)-5-((tert-butyldimethylsilyloxy) methyl)-1-((R)-4,4-dimethyl-2-oxocyclopentyl)-6-hydroxy-3-oxabicyclo[4.2.0]octan-

4-one (81). Samarium diiodide (1.36 ml, 0.1 M in THF, 0.136 mmol) was added quickly to a solution of 80 (24.9 mg, 0.0454 mmol) in a mixture of THF and t-butanol (4:1, 1.0 ml) at rt under argon. The solution was stirred at rt for 10 min before being exposed to air to quench the reaction. The resulting yellow solution was diluted with ethyl acetate and dichloromethane and poured into saturated NaHCO3 solution. The aqueous layer was back-extracted with dichloromethane. The combined organic layers were washed with 88 brine, dried over MgSO4, and concentrated. The residue was purified by flash column chromatography (silica gel, elution with hexanes/EtOAc 6:1) to afford 81 as a slightly yellow oil (10.0 mg, 41%). IR (neat, cm-1) 3314, 2953, 2927, 1748, 1514, 1249; 1H NMR

(500 MHz, CDCl3) δ 7.29 (d, J = 8.5 Hz, 2H), 6.90 (d, J = 8.5 Hz, 4H), 5.18 (s, 1H), 4.60

(d, J = 11.1 Hz, 1H), 4.42 (d, J = 11.1 Hz, 1H), 4.37 (d, J = 11.9 Hz, 1H), 4.20 (dd, J =

4.8, 10.5 Hz, 1H), 4.08-4.01 (m, 3H), 3.83 (s, 3H), 2.97 (dd, J = 8.2, 12.7 Hz, 1H), 2.84

(d, J = 5.3 Hz, 1H), 2.26 (d, J = 18.4 Hz, 1H), 2.20 (dd, J = 7.4, 14.1 Hz, 1H), 2.09-2.00

(m, 3H), 1.66 (t, J = 12.8 Hz, 1H), 1.21 (s, 3H), 1.07 (s, 3H), 0.92 (s, 9H), 0.11 (s, 6H);

13 C NMR (125 MHz, CDCl3) δ 221.2, 172.0, 159.5, 129.8, 129.6 (2C), 114.0 (2C), 76.7,

76.6, 72.5, 71.6, 59.3, 55.4, 54.4, 51.2, 50.7, 46.0, 40.5, 33.8, 32.8, 29.8, 27.4, 26.1 (3C),

+ 22 18.5 -5.3, -5.4; HRMS (ES) m/z M + Na calcd 555.2754, obsd 555.2761; [α]D – 4.8 (c

0.50, CHCl3).

(-)-(1R,5R,6S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((R)-4,4-dimethyl-2-

oxocyclopentyl)-6,7-dihydroxy-3-oxabicyclo[4.2.0]octan-4-one (82). Trifluoroacetic acid (0.10 ml) was added dropwise into a solution of 81 (10.0 mg, 0.0188 mmol) in 1.0 ml of dry dichloromethane at rt under argon. After 5 min, the reaction mixture was quenched by fast addition of saturated NaHCO3 solution. The mixture was diluted with ethyl acetate and dichloromethane. The organic layer was washed with brine, dried over

MgSO4, and concentrated. The residue was purified by flash column chromatography

(silica gel, elution with hexanes/EtOAc 5:1 with 1% ethanol) to afford 82 as a colorless oil (4.2 mg, 54%); IR (neat, cm-1) 3415, 2950, 2856, 1717, 1252, 1132; 1H NMR (500

MHz, CDCl3) δ 5.60 (s, 1H), 4.39 (d, J = 12.0 Hz, 1H), 4.23-4.21 (m, 1H), 4.16 (dd, J = 89 7.3, 10.2 Hz, 1H), 4.10 (dd, J = 4.5, 10.2 Hz, 1H), 4.06 (d, J = 12.0 Hz, 1H), 2.97 (dd, J =

8.2, 12.9 Hz, 1H), 2.88 (dd, J = 4.6, 7.3 Hz, 1H), 2.61 (d, J = 5.5 Hz, 1H), 2.32 (d, J =

20.0 Hz, 1H), 2.28 (dd, J = 7.6, 14.0 Hz, 1H), 2.12 (d, J = 18.6 Hz, 1H), 2.03 (ddd, J =

2.6, 8.2, 12.5 Hz, 1H), 1.84 (dd, J = 4.7, 14.0 Hz, 1H), 1.68 (t, J = 12.7 Hz, 1H), 1.24 (s,

13 3H), 1.10 (s, 3H), 0.92 (s, 9H), 0.13 (s, 3H), 0.12 (s, 3H); C NMR (125 MHz, CDCl3) δ

222.8, 171.6, 76.4, 72.6, 71.2, 59.5, 54.6, 50.4, 50.1, 46.0, 40.8, 34.7, 33.9, 29.8, 27.4,

26.0 (3C), 18.4, -5.4, -5.5; HRMS (ES) m/z (M + Na)+ calcd 435.2179, obsd 435.2170;

22 [α]D -43.5 (c 0.23, CHCl3).

(+)-(1S,7R)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((S)-4,4-dimethyl-2-

oxocyclopentyl)-7-hydroxy-3-oxabicyclo[4.2.0]oct-5-en-4-one (77) and (+)-(1S,7R)-5-

((tert-Butyldimethylsilyloxy)methyl)-1-((R)-4,4-dimethyl-2-oxocyclopentyl)-7-

hydroxy-3-oxabicyclo[4.2.0]oct-5-en-4-one (78) from 82. Thionyl chloride (0.90 µl,

0.012 mmol) was added slowly to a solution of 82 (4.2 mg, 0.010 mmol) and triethylamine (4.3 µl, 0.031 mmol) in 0.5 ml of dry dichloromethane at 0 oC under argon.

After 30 min at 0 oC, the solution was poured into a mixture of EtOAc, water, and a small amount of triethylamine. The organic layer was washed with brine, dried over MgSO4, and concentrated. The solid residue was used for the next step without further purification.

The solid residue was taken up in 0.5 ml of dry dichloromethane and cooled to 0 oC.

DBU (4.6 µl, 0.031 mmol) was added at 0 oC under argon. After 30 min at 0 oC, the mixture was loaded directly onto a silica gel column, eluted with hexanes/EtOAc (3.5:1, with 1% ethanol) to afford 77 (1.3 mg, 32%) and 78 (1.0 mg, 25%), both as white solids. 90 (S)-5-((tert-Butyldimethylsilyloxy)methyl)-1-((R)-4,4-dimethyl-2-

oxocyclopentyl)-3-oxabicyclo[4.2.0]octa-5,7-dien-4-one (85). Triflic anhydride (6.4 µl,

0.038 mmol) was added slowly to a solution of 77 (1.5 mg, 3.80 µmol) and pyridine (6.1

µl, 0.076 mmol) in dry dichloromethane (0.8 ml) at 0 °C under argon. After 15 min at 0 oC, isopropyl alcohol (2.9 µl, 0.038 mmol) was added. After 20 min at 0 °C, DBU (5.7

µl, 0.028 mmol) was added dropwise at 0 oC. After another 5 min, the reaction mixture was loaded onto a silica gel column, eluted with hexanes/ethyl acetate/dichloromethane

(5:1:1) to afford a slightly yellow solid, which was used directly in the next step. 1H

NMR (500 MHz, C6D6) δ 5.68 (d, J = 5.5 Hz, 1H), 4.69 (d, J = 14.0 Hz, 1H), 4.55 (d, J =

14.0 Hz, 1H), 3.93 (d, J = 11.4 Hz, 1H), 3.58 (d, J = 11.4 Hz, 1H), 3.11 (dd, J = 8.3, 13.3

Hz, 1H), 2.67 (d, J = 14.4 Hz, 1H), 1.84-1.77 (m, 2H), 1.72-1.60 (m, 2H), 1.55 (d, J =

18.6 Hz, 1H), 0.96 (s, 9H), 0.67 (s, 3H), 0.60 (s, 3H), 0.14 (s, 3H), 0.13 (s, 3H).

The above triflate was taken up in 0.2 ml of benzene. DBU (1.7 µl in 30 µl benzene, 11.4 µmol) was added at rt. After 2 h at rt, the mixture was loaded onto a silica gel column, eluted with hexanes/ethyl acetate/dichloromethane (6:1:1 with 0.5% triethylamine) to afford 85 (less polar, 0.5 mg, 35% over 2steps) and its epimer 84 (more polar, 0.3 mg, 21%), both as colorless oils;

1 For 22: H NMR (500 MHz, C6D6) δ 6.71 (d, J = 2.2 Hz, 1 H), 6.16 (d, J = 2.3

Hz, 1 H), 5.02 (d, J = 10.0 Hz, 1 H), 4.86 (d, J = 15.3 Hz, 1 H), 4.59 (d, J = 15.4 Hz, 1

H), 3.97 (d, J = 10.1 Hz, 1 H), 3.18 (dd, J = 9.4, 11.4 Hz, 1 H), 1.93 (d, J = 17.8 Hz, 1 H),

1.68 (d, J = 18.1 Hz, 1H), 1.53-1.49 (m, 2H), 1.03 (s, 9H), 0.83 (s, 3H), 0.63 (s, 3H), 0.13

(s, 3H), 0.12 (s, 3H); HRMS (ES) m/z (M+Na)+ calcd 399.1968, obsd 399.1986.

91 (+)-Fomannosin (1). Triethylamine trihydrofluoride (0.10 ml, 0.61 mmol) was

added dropwise into a solution of 85 (0.5 mg, 1.33 µmol) in acetonitrile (0.6 ml) at rt under argon, followed by the addition of triethylamine (0.03 ml, 0.213 mmol). After 35 min at rt, the reaction mixture was diluted with ether/dichloromethane (2/1), washed with

5% NaH2PO4 solution and brine, dried over MgSO4, and concentrated. The residue was purified by flash column chromatography (silica gel, ether/dichloromethane 1/1 with

0.5% triethylamine) to afford (+)-1 (0.2 mg, 57%) as a colorless oil; IR (film, cm-1) 3580,

1 1724, 1709, 1461, 1408; H NMR (500 MHz, CD2Cl2) δ 6.89 (d, J = 2.4 Hz, H-6, 1 H),

6.68 (d, J = 2.4 Hz, H-5, 1 H), 4.86 (d, J = 10.1 Hz, H-8, 1 H), 4.37 (dd, J = 5.5, 13.8 Hz,

H-1, 1 H), 4.30 (dd, J = 5.5, 13.8 Hz, H-1, 1 H), 4.25 (d, J = 10.1 Hz, H-8, 1 H), 3.15

(ddd, J = 1.2, 8.7, 12.3 Hz, H-9, 1 H), 2.19 (d, J = 17.4 Hz, H-12, 1 H), 1.92 (d, J = 18.4

Hz, H-12, 1 H), 1.74 (ddd, J = 2.4, 8.7, 12.8 Hz, H-10, 1 H), 1.61 (H-10, 1 H, overlap

13 with H2O peak), 1.15 (s, 3 H), 1.08 (s, 3 H); C NMR* (150 MHz, CD2Cl2) δ 218.37 (C-

13), 165.72 (C-3), 154.85 (C-4), 147.96 (C-5), 139.53 (C-6), 73.50 (C-8), 58.52 (C-1),

53.61 (C-12), 52.79 (C-7), 46.60 (C-9), 38.39 (C-10), 32.94 (C-11), 29.65 (CH3), 27.89

+ 22 (CH3); HRMS (ES) m/z (M+Na) calcd 285.1103, obsd 285.1119; [α]D +46.9 (c 0.02,

CH2Cl2).

______

*Due to small quantities of material, 13C data was obtained from HSQC and HMBC data. 92

BIBLIOGRAPHY

1. Bassett, C.; Sherwood, R. T.; Kepler, J. A.; Hamilton, P. B. Phytopathology 1967, 57, 1046.

2. Shain, L. Phytopathology 1967, 57, 1034.

3. Nozoe, S.; Matsumoto, H.; Urano, S. Tetrahedron Lett. 1971, 3125.

4. Kepler, J. A.; Wall, M. E.; Mason, J. E.; Basset, C.; McPhail, A. T.; Sim, G. A. J. Am. Chem. Soc. 1967, 89, 1260.

5. (a) Cane, D. E.; Nachbar, R. B. J. Am. Chem. Soc. 1978, 100, 3208. (b) Cane, D. E.; Nachbar, R. B. Tetrahedron Lett. 1976, 2097.

6. Cane, D. E.; Nachbar, R. B.; Clardy, J.; Finer, J. Tetrahedron Lett. 1977, 4277.

7. (a) Semmelhack, M. F.; Tomoda, S. J. Am. Chem. Soc. 1981, 103, 2427. (b) Semmelhack, M. F.; Tomoda, S.; Nagaoka, H.; Boettger, S. D.; Hurst, K. J. Am. Chem. Soc. 1982, 104, 747.

8. Miyano, K.; Ohfune, Y.; Azuma, S.; Matsumoto, T. Tetrahedron Lett. 1974, 1545.

9. (a) Kosugi, H.; Uda, H. Chem. Lett. 1977, 1491. (b) Kosugi, H.; Uda, H. Bull. Chem. Soc. Jpn. 1980, 53, 160.

10. McMorris, T. C.; Nair, M. S. R.; Anchel, M. J. Am. Chem. Soc. 1967, 89, 4562.

11. For synthesis of illudol, see: (a) Matsumoto, K.; Miyano, S.; Kagawa, S.; Yu, S.; Ogawa, J.; Ichibara, A. Tetrahedron Lett. 1971, 3521. (b) Semmelhack, M. F.; Tomoda, S.; Hurst, K. M. J. Am. Chem. Soc. 1980, 102, 7567. (c) Johnson, E. P.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1991, 113, 381.

12. (a) Ito, H.; Motoki, Y.; Taguchi, T.; Hanzawa, Y. J. Am. Chem. Soc. 1993, 115, 8835. (b) Hanzawa, Y.; Ito, H.; Taguchi, T. Synlett 1995, 299.

93 13. (a) Paquette, L. A.; Cuniere, N. Org. Lett. 2002, 4, 1927. (b) Paquette, L. A.; Kim, I. H.; Cuniere, N. Org. Lett. 2003, 5, 221.

14. Paquette, L. A.; Kang, H.-J. Tetrahedron 2004, 60, 1353.

15. Yang, J. Ph. D. Dissertation, The Ohio State University, 2003.

16. (a) Schmidt, O. T. Methods in Carbohydrate Chemistry 1963, 2, 320. (b) Hwang, C. K.; Li, W. S.; Nicolaou, K. C. Tetrahedron Lett. 1984, 25, 2295.

17. Just, G.; Luthe, C. Can. J. Chem. 1980, 58, 2286.

18. Arndt, F. Org. Synth. Coll. Vol. II, 1943, 165.

19. (a) Overman, L. E. Acc. Chem. Res. 1980 13, 218. (b) Patil, V. J. Tetrahedron Lett. 1996, 37, 1481.

20. Schlosser, M.; Jenny, T., Guggisberg, Y. Synlett 1990, 704.

21. Negishi, E.; Cederbaum, F. E.; Takahashi, T. Tetrahedron Lett. 1986, 27, 2829.

22. (a) Danheiser, R. L.; Savariar, S.; Cha, D. D. Org. Synth. 1990, 68, 32. (b) Johnston, B. D.; Czyzervska, E.; Oehlschlager, A. C. J. Org. Chem. 1987, 52, 3693. (c) Mehta, G.; Rao, H. S. P. Synth. Commun. 1985, 991. (d) Krepski, L. R.; Hassner, A. J. Org. Chem. 1978, 43, 2879. (e) Greene, A. E.; Luche, M. J.; Depres, J.-P. J. Am. Chem. Soc. 1983, 105, 2435.

23. (a) McMurry, J. E.; Lectka, T.; Rico, J. G. J. Org. Chem. 1989, 54, 3748. (b) McMurry, J. R. Chem. Rev. 1989, 89, 1513. (c) Lectka, T. In Active Metals, Furstner, A., Ed.; 1995, Wiley-VCH: Weinheim, p 85.

24. (a) McMurry, J. E.; Lectka, T.; Rico, J. G. Tetrahedron Lett. 1989, 30, 1169. (b) Robertson, G. M. In Comprehensive Organic Synthesis, Trost, B. M., Ed.; 1991, Pergamon Press: Oxford, p. 563.

25. Reviews: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18. (c) Fürstner, A. Angew. Chem. Int. Ed. 2000, 39, 3012. (d) Handbook of Metathesis 3 volumes, Grubbs, R. H. Ed., Wiley-VCH Verlag GmbH & Co., Weinheim, 2003. (d) Grubbs, R. H.; Tetrahedron 2004, 60, 7117. (e) Alkene Metathesis in Organic Synthesis; Furstner. A. Ed., Springer, Berlin, 1998.

26. (a) Veysoglu, T.; Mitscher, L. A.; Swayse, J. L. Synthesis 1980, 807. (b) Paquette, L. A.; Chang, J.; Liu, Z. J. Org. Chem. 2004, 69, 6441.

94 27. Bailey, W. F.; Punzalan, E. R. J. Org. Chem. 1990, 55, 5404.

28. (a) Maercker, A. Org. React. 1965, 14, 270. (b) Maryanoff, B. E.; Reits, A. B. Chem. Rev. 1989, 89, 863.

29. Pine, S. H. Org. React. 1993, 43, 1.

30. Matsubara, S.; Sugihara, M.; Utimoto, K. Syntlett. 1998, 313 and references therein.

31. Ager, D. J. Org. React. 1990, 38, 1.

32. Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org Lett. 1999, 1, 953.

33. Ho, T.-L. Tandem Organic Reactions, John Wiley & Sons, Inc., 1992, p. 416.

34. Minami, T.; Nishimura, K.; Hirao, I.; Suganuma, H.; Agawa, T. J. Org. Chem. 1982, 47, 2360.

35. (a). Krawczyk, H.; Synlett 1998, 1114. (b) Krawczyk, H.; Bodalski, R. J. Chem. Soc., Perkin Trans. 1, 2001, 1559.

36. Hiyashibayashi, S.; Shinko, K.; Ishizu, T.; Hashimoto, K.; Shirahama, H.; Nakata, M. Synlett 2000, 1306.

37. Oliver, S. F.; Högenauer, K.; Simic, O.; Antonello, A.; Smith, M. D.; Ley, S. V. Angew. Chem. Int. Ed. 2003, 42, 5996.

38. (a) Trost, B. M.; Caldwell, C. G.; Murayama, E.; Heissler, D. J. Org. Chem. 1983, 48, 3252. (b) Evans, D. A.; Gage, J. R.; Leighton, J. L. J. Am. Chem. Soc. 1992, 114, 9434.

39. Frigerio, M.; Santagostino, M. Tetrahedron Lett. 1994, 35, 8019.

40. (a) Jones, G. Org. React. 1967, 15, 204. (b) Smith, M. B.; March, J. March’s Advanced Organic Chemistry, 5th Ed.; John Wiley & Sons, Inc., 2001, p. 1225.

41. Beaulieu, P. L.; Deziel, R.; Brunet, M. L.; Moss, N.; Plante, R. U. S. (1998), 14 pp., Cont.-in-part of U. S. patent 5,574,015.

42. Crossland, R. K.; Servis, K. L. J. Org. Chem. 1970, 35, 3195.

43. Oikawa, Y.; Nishi, T.; Yonemitsu, O. Tetrahedron Lett. 1983, 24, 4037.

95 44. Friedrich-Bochnitschek, S.; Waldman, H.; Kunz, H. J. Org. Chem. 1989, 54, 751.

45. Perrotta, E.; Raffaelli, B.; Giannotti, D.; Harmat, N. J. S.; Nannicini, R.; Altamura, M. Synlett 1999, 144.

46. Thomas, R. M.; Mohan, G. H.; Iyengar, D. S. Tetrahedron Lett. 1997, 38, 4721.

47. Dessolin, M.; Guillerez, M.-G.; Thieriet, N.; Guibe, F.; Loffet, A. Tetrahedron Lett. 1995, 36, 5741.

48. Wissner, A.; Grudzinskas, C. J. Org. Chem. 1978, 43, 3972.

49. Imamoto, T.; Kodera, M.; Yokoyama, M. Bull. Chem. Soc. Jpn. 1982, 55, 2303.

50. Liu, H.-J.; Bukownik, R. R.; Pednekar, P. R. Syn. Commun. 1981, 11, 599.

51. (a) Takayama, H.; Fujiwara, R.; Kasai, Y.; Kitajima, M.; Aimi, N. Org. Lett. 2003, 5, 2967. (b) Fukuyama, T.; Lin, S.-C.; Li, L. J. Am. Chem. Soc. 1990, 112, 7050. (c) Eberle, M. K.; Jutzi-Eme, A.-M.; Nuninger, F. J. Org. Chem. 1994, 59, 7249.

52. Gribble, G. W.; In Encyclopedia of Reagents for Organic Synthesis, Paquette, L. A., Editor-in-chief, John Wiley & Sons, Inc., 1995, 4649.

53. (a) Nutaitis, C. F.; Gribble, G. W. Tetrahedron Lett. 1983, 24, 4287. (b) Gribble, G. W.; Nutatis, C. F. Org. Prep. Proced. Int. 1985, 17, 317.

54. Galatsis, P. In Encyclopedia of Reagents for Organic Synthesis, Paquette, L. A., Editor-in-chief, John Wiley & Sons, Inc., 1995, 3168.

55. (a) Fujii, H.; Hirano, N.; Uchiro, H.; Kawamura, K.; Nagase, H. Chem. Pharm. Bull. 2004, 52, 747. (b) Rabiczko, J.; Urbanczyk-Lipkowska, Z.; Chemielewski, M.; Tetrahedron 2002, 58, 1433.

56. Askin, D.; Angst, D.; Danishefsky, S. J. Org. Chem. 1987, 52, 622.

57. (a) Wang, Y.; Babirad, S. A.; Kishi, Y. J. Org. Chem. 1992, 57, 468. (b) Blakemore, P. R.; Kim, S.-K.; Schulze, V. K.; White, J. D.; Yokochi, A. F. T. J. Chem. Soc., Perkin Trans. 1, 2001, 1831.

58. (a) Yan, L.; Kahne, D. Synlett 1995, 523. (b) Bonzide, A.; Sauvé, G. Tetrahedron Lett. 1999, 40, 2883.

96 59. Myers, A. G.; Glatthar, R.; Hammond, M.; Harrington, P. M.; Kuo, E. Y.; Liang, J.; Schaus, S. E.; Wu, Y.; Xiang, J.-N.; J. Am. Chem. Soc. 2002, 124, 5380 and references therein.

60. (a) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94, 2483. (b) Bennani, Y. L.; Sharpless, K. B. Tetrahedron Lett. 1993, 34, 2083.

61. Mateos, A. F.; Barba, A. L.; Coca, G. P.; Gonzalez, R. R.; Hernandez, C. T. Synlett 1995, 409.

62. Blay, G.; Cardona, L.; Garcia, B.; Lahoz, L.; Pedro, J. R. J. Org. Chem. 2001, 66, 7700.

63. Reviews: (a) Pelter, A.; Smith, K.; Brown, H. C. Borane Reagents; Academic Press: N.Y. 1988. (b) Brown, H. C. Boranes in Organic Chemistry; Cornell University Press; Ithaca, NY, 1972. (c) Brown, H. C. Organic Syntheses via Boranes; Wiley: N.Y., 1975. (d) Cragg, G. M. L. Organoboranes in Organic Synthesis; Marcel Dekker: NY, 1973.

64. (a) Kabalka, G. W.; Maddox, J. T.; Shoup, T.; Bowers, K. R. Org. Syn. Coll. Vol. 9, 522. (b) Kabalka, G. W.; Shoup, T. M.; Goudgaon, N. M. J. Org. Chem. 1989, 54, 5930.

65. Bernardelli, P.; Moradei, O. M.; Friedrich, D.; Yang, J.; Gallou, F.; Dyck, B. P.; Doskotch, R. W.; Lange, R.; Paquette, L. A. J. Am. Chem. Soc. 2001, 123, 9021.

66. Corey, E. J.; Guzman-Perez, A.; Noe, M. C. J. Am. Chem. Soc. 1994, 116, 12109.

67. (a) Molander, G. A.; Hahn, G. J. Org. Chem. 1986, 51, 1135. (b) Hanessian S.; Girard, C.; Chiara, J. L. Tetrahedron Lett. 1992, 33, 573. (c) White J. D.; Somers, T. C. J. Am. Chem. Soc. 1987, 109, 4424.

68. (a) Burgess, E. M.; Penton, H. R. Jr.; Taylor, E. A.; Williams, W. M. Org. Syn. Coll. Vol. 6, 788. (b) Burgess, E. M.; Penton, H. R. Jr.; Taylor, E. A. J. Org. Chem. 1973, 38, 26. (c) Jendralla, H.; Jelich, K.; DeLucca, G.; Paquette, L. A. J. Am. Chem. Soc. 1986, 108, 3731.

69. (a) Hartung, R. Ph. D. Dissertation, 2005, The Ohio State University. (b) Naruta, Y.; Nagai, N.; Arita, Y.; Maruyama, K. J. Org. Chem. 1987, 52, 3956.

70. (a) Tius, M. A.; Hu, H.; Kawakami, J. K.; Busch-Petersen, J. J. Org. Chem. 1998, 63, 5971. (b) Dineen, T. A.; Roush, W. R. Org. Lett. 2004, 6, 2043.

APPENDIX

1H NMR SPECTRA

z H O M O 0 0 O 3 , 3 l C C D 2 C O , C 5 3 1 H

3 H z B C H M O M P 0 O 0 3 O , 3 l C C D 2 C O , 6 C 3 1 H

100

3 H z B C H M O M P 0 O 0 O 3 , 3 l C C D 2 C O O , C S 8 3 1 P H D B T

101

3 H z B C H M O M P 0 O 0 3 9 O , 1 3 l C D C 2 C , O O 9 S C 3 1 P H D B T

102

3 H B C z M O H P M O 0 0 O 3 , 3 l C D C O , S 0 P 2 D B T

103

3 H z B C H M O M P 0 O 0 O 3 , 3 l C D C O , S 1 2 P D B T

104

z O H M O 0 0 O 3 , 3 l C C 2 D O O C C S , 3 2 P H 2 D B T

105

z O H M O 0 O 0 3 , 3 l C D O C S , P 3 D 2 B T

106

e z M H O M H 0 O 0 O 3 , 3 l C D C O , S 4 P 2 D B T

107

e z M H O M H 0 O 0 3 O , 3 l C D C , O 5 S 2 P D B T

108

e B M z M O H P M O 0 0 O 3 , 3 l C D O C , S 6 P 2 D B T

109

S P z D H B M T O 0 0 H 3 O , 3 l C D C O , 7 B 2 M P

110

S P z D H B M T 0 O 0 H 3 O , 3 l C D C , O 8 B 2 M P

111

S P D B , z 7 T H S 2 O B M f T o 0 O r 0 e 3 h , t 3 e l C S D O B B C T M P

112

S P z D B H T M S O B 0 T 0 O 3 O H , 3 C l C D C O , B 9 2 M P

113

S P D z B H T S M O B 0 T 0 O 5 , 3 l C O D H C O , B 0 M 3 P

114

S P z D H B M T S O 0 B 0 T 3 O , 3 l C D O C O , 1 B 3 M P

115

S P z D H B T M S O B 0 T 0 3 O , 3 l C D C O , B 2 3 M P

116

S P z D H B T M S O B 0 0 T 5 O , 3 l C D C O , B 3 3 M P

117

z H S H O B M T 0 O 0 5 , 3 l C D O C B , M 0 P 4

118

2 ) t E O z ( H P O M 0 0 O 5 , S 3 O B l T C O D C , 1 4 O B M P

119

z H H O M H 0 O 0 5 , 3 l C D O C B , M 3 P 4

120

2 ) t E O ( z P H O M 0 0 O 3 , O 3 l H C O D C , 2 4 O B M P

121

2 ) t E O ( z P O H M 0 O 0 5 O , 3 l C O D C , 5 3 O B M P

122

z l l O H A 2 M O O 0 0 C 5 , 3 l C D O C , B 6 M 4 P

123

z H l l O M A 2 0 O 0 O 5 H C , P 3 l O M C H P D C O , 0 5

124

z H M O 0 O 0 5 , 3 l P O C M D P H C O , 1 5

125

z O H H O O M 0 0 O 5 , H 3 l C D O C B , M 8 P 5

126

z O H H M O O 0 0 5 O , H 3 l C D O C B , 9 M 5 P

127

z O H H M O O 0 0 5 , O 3 l H C D C O , B 0 M 6 P

128

S z B O H T M O O 0 0 5 O , 3 H l C D O C B , 1 M 6 P

129

S z B H O T M O O 0 0 5 , O 3 l H C D C O , B 2 M 6 P

130

z S H B O M T 0 O O 0 5 , 3 l O C H D C , O 4 H 6

131

z S H B O M T 0 O O 0 5 , 3 l C D C , O 7 H 6

132

z S B H O T M O O 0 0 5 , 3 l C D C O , s 8 M 6

133

S z B O H T M O O 0 0 H 5 O , O 3 H l C D O O C B H , 2 M 7 P

134

S z B O H T M O O 0 0 H 5 O , O 3 H l C D O O C B , 3 M 7 P

135

z S H B O M T 0 O O 0 5 , 3 l O H C H D C , O O 4 B 7 M P

136

z S H B O M T 0 O O 0 5 , 3 O l H H C D C O , O 5 H 7

137

z S H B O M T O O 0 0 5 , 3 O l H H C D C O O , 6 H 7

138

z S H B O M T 0 O O 0 5 , 3 l H C D C O , O 7 H 7

139

z S H B O T M O O 0 0 5 , 3 l H C D C O O , H 8 7

140

S z B H O T M O O 0 0 5 H , O 3 O l H C D C O O , B H 9 7 M P

141

S z B O T H O O M 0 0 H 5 O O , H 3 l C D O O C B , M 0 8 P

142

S B z O T H O O M 0 0 5 O H , H 3 l C D O O C B , M 1 8 P

143

z S H B O M T O O 0 0 5 , O 3 l H H C D C O O , 2 H 8

144

S z B H O T M O O 0 0 5 , H 6 D 6 C , O O f 3 T 8

145

z S H B O M T 0 O O 0 5 , 6 H D 6 C , 5 O 8

146

z n H o i t M O a 0 H c 0 i O O f 5 i r , u 2

l p C t H 2 s r D i f

C r , e O 1 t -

f ) A +

(

147

C H L T M O 0 H e 0 v O O i 5 t , a 2 r

l a C p H 2 e r D P C r , O 1 e t - f ) A + (

148

z O H

H O O , M 2

l 0 C 0 2

6 H D , C C , Q 1 O S H

149

O z H H O O , M 2 l

0 C 0 2 6 H D , C C , B 1 O M H

150